scene 1, in the ridiculous dialogue between Socrates and Strepsiades,

the latter announces a method which had occurred to him to pay his debts. “You know,” says he, “the beautiful transparent stone used for kindling fire.” “Do you mean glass (τον ὕαλον, _ton hyalon_)?” replied Socrates. “I do,” was the answer. He then describes how he would destroy the writings by means of it, and thus defraud his creditors. Now this comedy was acted about four hundred and twenty-three years before the beginning of the Christian era. The story related by Pliny, respecting the discovery of this beautiful and important substance, is well known. Some Phœnician merchants, in a ship loaded with carbonate of soda from Egypt, stopped, and went ashore on the banks of the river Belus: having nothing to support their kettles while they were dressing their food, they employed lumps of carbonate of soda for that purpose. The fire was strong enough to fuse some of this soda, and to unite it with the fine sand of the river Belus: the consequence of this was the formation of glass.[74] Whether this story be entitled to credit or not, it is clear that the discovery must have originated in some such accident. Pliny’s account of the manufacture of glass, like his account of every other manufacture, is very imperfect: but we see from it that in his time they were in the habit of making coloured glasses; that colourless glasses were most highly prized, and that glass was rendered colourless then as it is at present, by the addition of a certain quantity of oxide of manganese. Colourless glass was very high priced in Pliny’s time. He relates, that for two moderate-sized colourless drinking-glasses the Emperor Nero paid 6000 sistertii, which is equivalent to 25_l._ of our money.

[73] Job xxviii. 17.

[74] Plinii Hist. Nat. xxxvi. 26.

Pliny relates the story of the man who brought a vessel of malleable glass to the Emperor Tiberius, and who, after dimpling it by dashing it against the floor, restored it to its original shape and beauty by means of a hammer; Tiberius, as a reward for this important discovery, ordered the artist to be executed, in order, as he alleged, to prevent gold and silver from becoming useless. But though Pliny relates this story, it is evident that he does not give credit to it; nor does it deserve credit. We can assign no reason why malleable substances may not be transparent; but all of them hitherto known are opaque. Chloride of silver, chloride of lead and iron constitute no exception, for they are not malleable, though by peculiar contrivances they may be extended; and their transparency is very imperfect.

Many specimens of the coloured glasses made by the ancients still remain, particularly the beads employed as ornaments to the Egyptian mummies. Of these ancient glasses several have been examined chemically by Klaproth, Hatchett, and some other individuals, in order to ascertain the substances employed to give colour to the glass. The following are the facts that have been ascertained:

1. _Red glass._ This glass was opaque, and of a lively copper-red colour. It was probably the kind of red glass to which Pliny gave the name of hæmatinon. Klaproth analyzed it, and obtained from 100 grains of it the following constituents:

Silica 71 Oxide of lead 10 Oxide of copper 7·5 Oxide of iron 1 Alumina 2·5 Lime 1·5 ----- 93·5[75]

[75] Beitrage, vi. 140.

No doubt the deficiency was owing to the presence of an alkali. From this analysis we see that the colouring matter of this glass was _red oxide of copper_.

2. _Green glass._ The colour was light verdigris-green, and the glass, like the preceding, was opaque. The constituents from 100 grains were,

Silica 65 Black oxide of copper 10 Oxide of lead 7·5 Oxide of iron 3·5 Lime 6·5 Alumina 5·5 ----- 98·0[76]

[76] Ibid., p. 142.

Thus it appears that both the red and green glass are composed of the same ingredients, though in different proportions. Both owe their colour to copper. The red glass is coloured by the red oxide of that metal; the green by the black oxide, which forms green-coloured compounds, with various acids, particularly with carbonic acid and with silica.

3. _Blue glass._ The variety analyzed by Klaproth had a sapphire-blue colour, and was only translucent on the edges. The constituents from 100 grains of it were,

Silica 81·5 Oxide of iron 9·5 Alumina 1·5 Oxide of copper 0·5 Lime 0·25 ----- 93·25[77]

[77] Beitrage, p. 144.

From this analysis it appears that the colouring matter of this glass was oxide of iron: it was therefore analogous to the lapis lazuli, or ultramarine, in its nature.

Davy, as has been formerly noticed, found another blue glass, or frit, coloured by means of copper; and he showed that the blue paint of the ancients was often made from this glass, simply by grinding it to powder.

Klaproth could find no cobalt in the blue glass which he examined; but Davy found the transparent blue glass vessels, which are along with the vases, in the tombs of Magna Græcia, tinged with cobalt; and he found cobalt in all the transparent ancient blue glasses with which Mr. Millingen supplied him. The mere fusion of these glasses with alkali, and subsequent digestion of the product with muriatic acid, was sufficient to produce a sympathetic ink from them.[78] The transparent blue beads which occasionally adorn the Egyptian mummies have also been examined, and found coloured by cobalt. The opaque glass beads are all tinged by means of oxide of copper. It is probable from this that all the transparent blue glasses of the ancients were coloured by cobalt; yet we find no allusion to cobalt in any of the ancient authors. Theophrastus says that copper (χαλκος, _chalcos_) was used to give glass a fine colour. Is it not likely that the impure oxide of cobalt, in the state in which they used it, was confounded by them with χαλκος (_chalcos_)?

[78] Phil. Trans. 1815, p. 108.

IV.--VASA MURRHINA.

The Romans obtained from the east, and particularly from Egypt, a set of vessels which they distinguished by the name of _vasa murrhina_, and which were held by them in very high estimation. They were never larger than to be capable of containing from about thirty-six to forty cubic inches. One of the largest size cost, in the time of Pliny, about 7000_l._ Nero actually gave for one 3000_l._ They began to be known in Rome about the latter days of the republic. The first six ever seen in Rome were sent by Pompey from the treasures of Mithridates. They were deposited in the temple of Jupiter in the capitol. Augustus, after the battle of Actium, brought one of these vessels from Egypt, and dedicated it also to the gods. In Nero’s time they began to be used by private persons; and were so much coveted that Petronius, the favourite of that tyrant, being ordered for execution, and conceiving that his death was owing to a wish of Nero to get possession of a vessel of this kind which he had, broke the vessel in pieces in order to prevent Nero from gaining his object.

There appear to have been two kinds of these vasa murrhina; those that came from Asia, and those that were made in Egypt. The latter were much more common, and much lower priced than the former, as appears from various passages in Martial and Propertius.

Many attempts have been made, and much learning displayed by the moderns to determine the nature of these celebrated vessels; but in general these attempts were made by individuals too little acquainted with chemistry and with natural history in general to qualify them for researches of so difficult a nature. Some will have it that they consisted of a kind of gum; others that they were made of glass; others, of a particular kind of shell. Cardan and Scaliger assure us that they were _porcelain_ vessels; and this opinion was adopted likewise by Whitaker, who supported it with his usual violence and arrogance. Many conceive them to have been made of some precious stone, some that they were of _obsidian_; Count de Veltheim thinks that they were made of the Chinese _agalmatolite_, or _figure stone_; and Dr. Hager conceives that they were made from the Chinese stone _yu_. Bruckmann was of opinion that these vessels were made of sardonyx, and the Abbé Winckelmann joins him in the same conclusion.

Pliny informs us that these vasa murrhina were formed from a species of stone dug out of the earth in Parthia, and especially in Carimania, and also in other places but little known.[79] They must have been very abundant at Rome in the time of Nero; for Pliny informs us that a man of consular rank, famous for his collection of vasa murrhina, having died, Nero forcibly deprived his children of these vessels, and they were so numerous that they filled the whole inside of a theatre, which Nero hoped to have seen filled with Romans when he came to it to sing in public.

[79] Plinii Hist. Nat. xxxvii. 2.

It is clear that the value of these vessels depended on their size. Small vessels bore but a small price, while that of large vessels was very high; this shows us that it must have been difficult to procure a block of the stone out of which they were cut, of a size sufficiently great to make a large vessel.

These vessels were so soft that an impression might be made upon them with the teeth; for Pliny relates the story of a man of consular rank, who drank out of one, and was so enamoured with it that he bit pieces out of the lip of the cup: “Potavit ex eo ante hos annos consularis, ob amorem abraso ejus margine.” And what is singular, the value of the cup, so far from being injured by this abrasure, was augmented: “ut tamen injuria ilia pretium augeret; neque est hodie murrhini alterius præstantior indicatura.”[80] It is clear from this that the matter of these vessels was neither rock crystal, agate, nor any precious stone whatever, all of which are too hard to admit of an impression from the teeth of a man.

[80] Plinii Hist. Nat. xxxvii. 2.

The lustre was vitreous to such a degree that the name _vitrum murrhinum_ was given to the artificial fabric, in Egypt.

The splendour was not very great, for Pliny observes, “Splendor his sine viribus nitorque verius quam splendor.”

The colours, from their depth and richness, were what gave these vessels their value and excited admiration. The principal colours were purple and white, disposed in undulating bands, and usually separated by a third band, in which the two colours being mixed, assumed the tint of flame: “Sed in pretio varietas colorum, subinde circumagentibus se maculis in purpuram candoremque, et tertium ex utroque ignescentem, velut per transitum coloris, purpura rubescente, aut lacte candescente.”

Perfect transparency was considered as a defect, they were merely translucent; this we learn not merely from Pliny, but from the following epigram of Martial:

Nos bibimus vitro, tu murra, Pontice: quare? Prodat perspicuus ne duo vina calix.

Some specimens, and they were the most valued, exhibited a play of colour like the rainbow: Pliny says they were very commonly spotted with “sales, verrucæque non eminentes, sed ut in corpore etiam plerumque sessiles.” This, no doubt, refers to foreign bodies, such as grains of pyrites, antimony, galena, &c., which were often scattered through the substances of which the vessels were made.

Such are all the facts respecting the vasa murrhina to be found in the writings of the ancients; they all apply to fluor spar, and to nothing else; but to it they apply so accurately as to leave little doubt that they were in reality vessels of fluor spar, similar to those at present made in Derbyshire.[81]

[81] This opinion was first formed by Baron Born, and stated in his Catalogue of Minerals in M. E. Raab’s collection, i. 356. But the evidences in favour of it have been brought forward with great clearness and force by M. Roziere. See Jour. de Min. xxxvi. 193.

The artificial vasa murrhina made at Thebes, in Egypt, were doubtless of glass, coloured to imitate fluor spar as much as possible, and having the semi-transparency which distinguishes that mineral. The imitations being imperfect, these factitious vessels were not much prized nor sought after by the Romans, they were rather distributed among the Arabians and Ethiopians, who were supplied with glass from Egypt.

Rock crystal is compared by Pliny with the stone from which the vasa murrhina were made; the former, in his opinion, had been coagulated by cold, the latter by heat. Though the ancients, as we have seen, were acquainted with the method of colouring glass, yet they prized colourless glass highest on account of its resemblance to rock crystal; cups of it, in Pliny’s time, had supplanted those of silver and gold; Nero gave for a crystal cup 150,000 sistertii, or 625_l._

V.--DYEING AND CALICO-PRINTING.

Very little has been handed down by the ancients respecting the processes of dyeing. It is evident, from Pliny, that they were acquainted with madder, and that preparations of iron were used in the black dyes. The most celebrated dye of all, the _purple_, was discovered by the Tyrians about fifteen centuries before the Christian era. This colour was given by various kinds of shellfish which inhabit the Mediterranean. Pliny divides them into two genera; the first, comprehending the smaller species, he called _buccinum_, from their resemblance to a hunting-horn; the second, included those called _purpura_: Fabius Columna thinks that these were distinguished also by the name of _murex_.

These shellfish yielded liquor of different shades of colour; they were often mixed in various proportions to produce particular shades of colour. One, or at most two drops of this liquor were obtained from each fish, by extracting and opening a little reservoir placed in the throat. To avoid this trouble, the smaller species were generally bruised whole, in a mortar; this was also frequently done with the large, though the other liquids of the fish must have in some degree injured the colour. The liquor, when extracted, was mixed with a considerable quantity of salt to keep it from putrifying; it was then diluted with five or six times as much water, and kept moderately hot in leaden or tin vessels, for eight or ten days, during which the liquor was often skimmed to separate all the impurities. After this, the wool to be dyed, being first well washed, was immersed and kept therein for five hours; then taken out, cooled, and again immersed, and continued in the liquor till all the colour was exhausted.[82]

[82] Plinii Hist. Nat. ix. 38.

To produce particular shades of colour, carbonate of soda, urine, and a marine plant called _fucus_, were occasionally added: one of these colours was a very dark reddish violet--“Nigrantis rosæ colore sublucens.”[83] But the most esteemed, and that in which the Tyrians particularly excelled, resembled coagulated blood--“laus ei summa in colore sanguinis concreti, nigricans aspectu, idemque suspectu refulgens.”[84]

[83] Ibid., ix. 36.

[84] Plinii Hist. Nat. ix. c. 38.

Pliny says that the Tyrians first dyed their wool in the liquor of the purpura, and afterwards in that of the buccinum; and it is obvious from Moses that this purple was known to the Egyptians in his time.[85] Wool which had received this double Tyrian dye (_dia bapha_) was so very costly that, in the reign of Augustus, it sold for about 36_l._ the pound. But lest this should not be sufficient to exclude all from the use of it but those invested with the very highest dignities of the state, laws were made inflicting severe penalties, and even death, upon all who should presume to wear it under the dignity of an emperor. The art of dyeing this colour came at length to be practised by a few individuals only, appointed by the emperors, and having been interrupted about the beginning of the twelfth century all knowledge of it died away, and during several ages this celebrated dye was considered and lamented as an irrecoverable loss.[86] How it was afterwards recovered and made known by Mr. Cole, of Bristol, M. Jussieu, M. Reaumur, and M. Duhamel, would lead us too far from our present object, were we to relate it: those who are interested in the subject will find an historical detail in Bancroft’s work on Permanent Colours, just referred to.

[85] Exodus xxv. 4.

[86] See Bancroft on Permanent Colours, i. 79.

There is reason to suspect that the Hebrew word translated _fine linen_ in the Old Testament, and so celebrated as a production of Egypt, was in reality _cotton_, and not linen. From a curious passage in Pliny, there is reason to believe that the Egyptians in his time, and probably long before, were acquainted with the method of calico-printing, such as is still practised in India and the east. The following is a literal translation of the passage in question:

“There exists in Egypt a wonderful method of dyeing. The white cloth is stained in various places, not with dye stuffs, but with substances which have the property of absorbing (_fixing_) colours, these applications are not visible upon the cloth; but when they are dipped into a hot caldron of the dye they are drawn out an instant after dyed. The remarkable circumstance is, that though there be only one dye in the vat, yet different colours appear upon the cloth; nor can the colour be afterwards removed.”[87]

[87] Plinii Hist. Nat. xxxv. 11.

It is evident enough that these substances applied were different mordants which served to fix the dye upon the cloth; the nature of these mordants cannot be discovered, as nothing specific seems to have been known to Pliny. The modern mordants are solutions of alumina; of the oxide of tin, oxide of iron, oxide of lead, &c.: and doubtless these, or something equivalent to these, were the substances employed by the ancients. The purple dye required no mordant, it fixed itself to the cloth in consequence of the chemical affinity which existed between them. Whether indigo was used by the ancients as a dye does not appear, but there can be no doubt, at least, that its use was known to the Indians at a very remote period.

From these facts, few as they are, there can be little doubt that dyeing, and even calico-printing, had made considerable progress among the ancients; and this could not have taken place without a considerable knowledge of colouring matters, and of the mordants by which these colouring matters were fixed. These facts, however, were probably but imperfectly understood, and could not be the means of furnishing the ancients with any accurate chemical knowledge.

VI.--SOAP.

Soap, which constitutes so important and indispensable an article in the domestic economy of the moderns, was quite unknown to the ancient inhabitants of Asia, and even of Greece. No allusion to it occurs in the Old Testament. In Homer, we find Nausicaa, the daughter of the King of the Phæacians, using nothing but water to wash her nuptial garments:

They seek the cisterns where Phæacian dames Wash their fair garments in the limped streams; Where gathering into depth from falling rills, The lucid wave a spacious bason fills. The mules unharness’d range beside the main, Or crop the verdant herbage of the plain. Then emulous the royal robes they lave, And plunge the vestures in the cleansing wave. _Odyssey_, vi. 1. 99.

We find, in some of the comic poets, that the Greeks were in the habit of adding wood-ashes to water to make it a better detergent. Wood-ashes contain a certain portion of carbonate of potash, which of course would answer as a detergent; though, from its caustic qualities, it would be injurious to the hands of the washerwomen. There is no evidence that carbonate of soda, the _nitrum_ of the ancients, was ever used as a detergent; this is the more surprising, because we know from Pliny that it was employed in dyeing, and one cannot see how a solution of it could be employed by the dyers in their processes without discovering that it acted powerfully as a detergent.

The word _soap_ (_sapo_) occurs first in Pliny. He informs us that it was an invention of the Gauls, who employed it to render their hair shining; that it was a compound of wood-ashes and tallow, that there were two kinds of it, _hard_ and _soft_ (_spissus et liquidus_); and that the best kind was made of the ashes of the beech and the fat of goats. Among the Germans it was more employed by the men than the women.[88] It is curious that no allusion whatever is made by Pliny to the use of soap as a detergent; shall we conclude from this that the most important of all the uses of soap was unknown to the ancients?

[88] Plinii Hist. Nat. xxviii. 12. The passage of Pliny is as follows: “Prodest et sapo; Gallorum hoc inventum rutilandis capillis ex sevo et cinere. Optimus fagino et caprino, duobus modis, spissus et liquidus: uterque apud Germanos majore in usu viris quam feminis.”

It was employed by the ancients as a pomatum; and, during the early part of the government of the emperors, it was imported into Rome from Germany, as a pomatum for the young Roman beaus. Beckmann is of opinion that the Latin word _sapo_ is derived from the old German word _sepe_, a word still employed by the common people of Scotland.[89]

[89] Hist. of Inventions, iii. 239.

It is well known that the state of soap depends upon the alkali employed in making it. _Soda_ constitutes a _hard_ soap, and _potash_ a _soft_ soap. The ancients being ignorant of the difference between the two alkalies, and using wood-ashes in the preparation of it, doubtless formed soft soap. The addition of some common salt, during the boiling of the soap, would convert the soft into hard soap. As Pliny informs us that the ancients were acquainted both with hard and soft soap, it is clear that they must have followed some such process.

VII.--STARCH.

The manufacture of starch was known to the ancients. Pliny informs us that it was made from wheat and from _siligo_, which was probably a variety or sub-species of wheat. The invention of starch is ascribed by Pliny to the inhabitants of the island of Chio, where in his time the best starch was still made. Pliny’s description of the method employed by the ancients of making starch is tolerably exact. Next to the China starch that of Crete was most celebrated; and next to it was the Egyptian. The qualities of starch were judged of by the weight; the lightest being always reckoned the best.

VIII.--BEER.

That the ancients were acquainted with wine is universally known. This knowledge must have been nearly coeval with the origin of society; for we are informed in Genesis that Noah, after the flood, planted a vineyard, and made wine, and got intoxicated by drinking the liquid which he had manufactured.[90] Beer also is a very old manufacture. It was in common use among the Egyptians in the time of Herodotus, who informs us that they made use of a kind of wine made from barley, because no vines grew in their country.[91] Tacitus informs us, that in his time it was the drink of the Germans.[92] Pliny informs us that it was made by the Gauls, and by other nations. He gives it the name of _cerevisia_ or _cervisia_; the name obviously alluding to the grain from which it was made.

[90] Genesis ix. 20.

[91] “Oinô d’ ek kritheôn pepoiêmenô diachreontai; ou gar sphi eisi en tê chôrê ampeloi.” Euterpe chap. 77.

[92] De Moribus Germanorum, c. 23. “Potui humor ex hordeo aut frumento in quandam similitudinem vini corruptus.”

But though the ancients seem acquainted with both wine and beer, there is no evidence of their having ever subjected these liquids to distillation, and of having collected the products. This would have furnished them with ardent spirits or alcohol, of which there is every reason to believe they were entirely ignorant. Indeed, the method employed by Dioscorides to obtain mercury from cinnabar, is a sufficient proof that the true process of distillation was unknown to them. He mixed cinnabar with iron filings, put the mixture into a pot, to the top of which a cover of stoneware was luted. Heat was applied to the pot, and when the process was at an end, the mercury was found adhering to the inside of the cover. Had they been aware of the method of distilling the quicksilver ore into a receiver, this imperfect mode of collecting only a small portion of the quicksilver, separated from the cinnabar, would never have been practised. Besides, there is not the smallest allusion to ardent spirits, either in the writings of the poets, historians, naturalists, or medical men of ancient Greece; a circumstance not to be accounted for had ardent spirits been known, and applied even to one-tenth of the uses to which they are put by the moderns.

IX.--STONEWARE.

The manufacture of stoneware vessels was known at a very early period of society. Frequent allusions to the potter’s wheel occur in the Old Testament, showing that the manufacture must have been familiar to the Jewish nation. The porcelain of the Chinese boasts of a very high antiquity indeed. We cannot doubt that the processes of the ancients were similar to those of the moderns, though I am not aware of any tolerably accurate account of them in any ancient author whatever.

Moulds of plaster of Paris were used by the ancients to take casts precisely as at present.[93]

[93] Plinii Hist. Nat. xxxv. 12.

The sand of Puzzoli was used by the Romans, as it is by the moderns, to form a mortar capable of hardening under water.

Pliny gives us some idea of the Roman bricks, which are known to have been of an excellent quality. There were three sizes of bricks used by the Romans.

1. Lydian, which were 1½ foot long and 1 foot broad.

2. Tetradoron, which was a square of 16 inches each side.

3. Pentadoron, which was a square, each side of which was 20 inches long.

Doron signifies the palm of the hand: of course it was equivalent to 4 inches.

X.--PRECIOUS STONES AND MINERALS.

Pliny has given a pretty detailed description of the precious stones of the ancients; but it is not very easy to determine the specific minerals to which he alludes.

1. The description of the diamond is tolerably precise. It was found in Ethiopia, India, Arabia, and Macedonia. But the Macedonian diamond, as well as the adamas cyprius and siderites, were obviously not diamonds, but soft stones.

2. The _emerald_ of the ancients (_smaragdus_) must have varied in its nature. It was a green, transparent, hard stone; and, as colour was the criterion by which the ancients distinguished minerals and divided them into species, it is obvious that very different minerals must have been confounded together, under the name of emerald. Sapphire, beryl, doubtless fluor spar when green, and probably even serpentine, nephrite, and some ores of copper, seem to have occasionally got the same name. There is no reason to believe that the _emerald_ of the moderns was known before the discovery of America. At least it has been only found in modern times in America. Some of the emeralds described by Pliny as losing their colour by exposure to the sun, must have been fluor spars. There is a remarkably deep and beautiful green fluor spar, met with some years ago in the county of Durham, in one of the Weredale mines that possesses this property. The emeralds of the ancients were of such a size (13½ feet, large enough to be cut into a pillar), that we can consider them in no other light than as a species of rock.

3. Topaz of the ancients had a green colour, which is never the case with the modern topaz. It was found in the island Topazios, in the Red Sea.[94] It is generally supposed to have been the _chrysolite_ of the moderns. But Pliny mentions a statue of it six feet long. Now chrysolite never occurs in such large masses. Bruce mentions a green substance in an emerald island in the Red Sea, not harder than glass. Might not this be the emerald of the ancients?

[94] The word topazo is said by Pliny to signify, in the language of the Troglodytes, _to seek_.

4. _Calais_, from the locality and colour was probably the Persian turquoise, as it is generally supposed to be.

5. Whether the _prasius_ and _chrysoprasius_ of Pliny were the modern stones to which these names are given, we have no means of determining. It is generally supposed that they are, and we have no evidence to the contrary.

6. The _chrysolite_ of Pliny is supposed to be our _topaz_: but we have no other evidence of this than the opinion of M. Du Tems.

7. _Asteria_ of Pliny is supposed by Saussure to be our sapphire. The lustre described by Pliny agrees with this opinion. The stone is said to have been very hard and colourless.

8. _Opalus_ seems to have been our _opal_. It is called, Pliny says, _pæderos_ by many, on account of its beauty. The Indians called it _sangenon_.

9. _Obsidian_ was the same as the mineral to which we give that name. It was so called because a Roman named Obsidianus first brought it from Egypt. I have a piece of obsidian, which the late Mr. Salt brought from the locality specified by Pliny, and which possesses all the characters of that mineral in its purest state.

10. _Sarda_ was the name of _carnelian_, so called because it was first found near Sardis. The _sardonyx_ was also another name for _carnelian_.

11. Onyx was a name sometimes given to a rock, _gypsum_; sometimes it was a light-coloured _chalcedony_. The Latin name for chalcedony was _carchedonius_, so called because Carthage was the place where this mineral was exposed to sale. The Greek name for Carthage was Καρχηδων (_carchedon_).

12. _Carbunculus_ was the garnet; and _anthrax_ was a name for another variety of the same mineral.

13. The _oriental amethyst_ of Pliny was probably a sapphire. The fourth species of amethyst described by Pliny, seems to have been our amethyst. Pliny derives the name from α (_a_) and μυθη (_mythe_), _wine_, because it has not quite the colour of wine. But the common derivation is from α and μυθυω, _to intoxicate_, because it was used as an amulet to prevent intoxication.

14. The _sapphire_ is described by Pliny as always opaque, and as unfit for engraving on. We do not know what it was.

15. The _hyacinth_ of Pliny is equally unknown. From its name it was obviously of a blue colour. Our hyacinth has a reddish-brown colour, and a great deal of hardness and lustre.

16. The _cyanus_ of Pliny may have been our _cyanite_.

17. _Astrios_ agrees very well, as far as the description of Pliny goes, with the variety of felspar called _adularia_.

18. _Belioculus_ seems to have been our _catseye_.

19. _Lychnites_ was a violet-coloured stone, which became electric by heat. Unless it was a _blue tourmalin_, I do not know what it could be.

20. The _jasper_ of the ancients was probably the same as ours.

21. _Molochites_ may have been our _malachite_. The name comes from the Greek word μολοχη, _mallow_, or _marshmallow_.

22. Pliny considers _amber_ as the juice of a tree concreted into a solid form. The largest piece of it that he had ever seen weighed 13 lbs. Roman weight, which is nearly equivalent to 9¾ lbs. avoirdupois. _Indian amber_, of which he speaks, was probably _copal_, or some transparent resin. It may be dyed, he says, by means of _anchusa_ and the _fat of kids_.

23. _Lapis specularis_ was foliated sulphate of lime, or selenite.

24. _Pyrites_ had the same meaning among the ancients that it has among the moderns; at least as far as iron pyrites or bisulphuret of iron is concerned. Pliny describes two kind of pyrites; namely, the _white_ (_arsenical pyrites_), and the _yellow_ (iron pyrites). It was used for striking fire with steel, in order to kindle tinder. Hence the name _pyrites_ or _firestone_.

25. _Gagates_, from the account given of it by Pliny, was obviously pit-coal or jet.

26. _Marble_ had the same meaning among the ancients that it has among the moderns. It was sawed by the ancients into slabs, and the action of the saw was facilitated by a sand brought for the purpose from Ethiopia and the isle of Naxos. It is obvious that this sand was powdered corundum, or emery.

27. _Creta_ was a name applied by the ancients not only to chalk, but to _white clay_.

28. _Melinum_ was an _oxide of iron_. Pliny gives a list of one hundred and fifty-one species of stones in the order of the alphabet. Very few of the minerals contained in this list can be made out. He gives also a list of fifty-two species of stones, whose names are derived from a fancied resemblance which the stones are supposed to bear to certain parts of animals. Of these, also, very few can be made out.

XI.--MISCELLANEOUS OBSERVATIONS.

The ancients seem to have been ignorant of the nature and properties of air, and of all gaseous bodies. Pliny’s account of air consists of a single sentence: “Aër densatur nubibus; furit procellis.” “Air is condensed in clouds, it rages in storms.” Nor is his description of water much more complete, since it consists only of the following phrases: “Aquæ subeunt in imbres, rigescunt in grandines, tumescunt in fluctus, præcipitantur in torrentes.”[95] “Water falls in showers, congeals in hail, swells in waves, and rushes down in torrents.” In the thirty-eighth chapter of the second book, indeed, he professes to treat of _air_; but the chapter contains merely an enumeration of meteorological phenomena, without once touching upon the nature and properties of air.

[95] Plinii Hist. Nat. ii. 63.

Pliny, with all the philosophers of antiquity, admitted the existence of the four elements, fire, air, water, and earth; but though he enumerates these in the fifth chapter of his first book, he never attempts to explain their nature or properties. Earth, among the ancients, had two meanings, namely, the planet on which we live, and the soil upon which vegetables grow. These two meanings still exist in common language. The meaning afterwards given to the _term_, earth, by the chemists, did not exist in the days of Pliny, or, at least, was unknown to him; a sufficient proof that chemistry, in his time, had made no progress as a science; for some notions respecting the properties and constituents of those supposed four elements must have constituted the very foundation of scientific chemistry.

The ancients were acquainted with none of the acids which at present constitute so numerous a tribe, except _vinegar_, or _acetic acid_; and even this acid was not known to them in a state of purity. They knew none of the saline bases, except lime, soda, and potash, and these very imperfectly. Of course the whole tribe of salts was unknown to them, except a very few, which they found ready formed in the earth, or which they succeeded in forming by the action of vinegar on lead and copper. Hence all that extensive and most important branch of chemistry, consisting of the combinations of the acids and bases, on which scientific chemistry mainly depends, must have been unknown to them.

Sulphur occurring native in large quantities, and being remarkable for its easy combustibility, and its disagreeable smell when burning, was known in the very earliest ages. Pliny describes four kinds of sulphur, differing from each other, probably, merely in their purity. These were

1. Sulphur vivum, or apyron. It was dug out of the earth solid, and was doubtless pure, or nearly so. It alone was used in medicine.

2. Gleba--used only by fullers.

3. Egula--used also by fullers.

Pliny says, it renders woollen stuffs white and soft. It is obvious from this, that the ancients knew the method of bleaching flannel by the fumes of sulphur, as practised by the moderns.

4. The fourth kind was used only for sulphuring matches.

Sulphur, in Pliny’s time, was found native in the Æolian islands, and in Campania. It is curious that he never mentions Sicily, whence the great supply is drawn for modern manufacture.

In medicine, it seems to have been only used externally by the ancients. It was considered as excellent for removing eruptions. It was used also for fumigating.

The word _alumen_, which we translate _alum_, occurs often in Pliny; and is the same substance which the Greeks distinguished by the name of στυπτηρια (_stypteria_). It is described pretty minutely by Dioscorides, and also by Pliny. It was obviously a natural production, dug out of the earth, and consequently quite different from our alum, with which the ancients were unacquainted. Dioscorides says that it was found abundantly in Egypt; that it was of various kinds, but that the slaty variety was the best. He mentions also many other localities. He says that, for medical purposes, the most valued of all the varieties of alumen were the _slaty_, the _round_, and the _liquid_. The slaty alumen is very white, has an exceedingly astringent taste, a strong smell, is free from stony concretions, and gradually cracks and emits long capillary crystals from these rifts; on which account it is sometimes called _trichites_. This description obviously applies to a kind of slate-clay, which probably contained pyrites mixed with it of the decomposing kind. The capillary crystals were probably similar to those crystals at present called _hair-salt_ by mineralogists, which exude pretty abundantly from the shale of the coal-beds, when it has been long exposed to the air. _Hair-salt_ differs very much in its nature. Klaproth ascertained by analysis, that the _hair-salt_ from the quicksilver-mines in Idria is sulphate of magnesia, mixed with a small quantity of sulphate of iron.[96] The _hair-salt_ from the abandoned coal-pits in the neighbourhood of Glasgow is a double salt, composed of sulphate of alumina, and sulphate of iron, in definite proportions; the composition being

[96] Beitrage, iii. 104.

1 atom protosulphate of iron, 1½ atom sulphate of alumina, 15 atoms water.

I suspect strongly that the capillary crystals from the schistose alumen of Dioscorides were nearly of the same nature.

From Pliny’s account of the uses to which alumen was applied, it is quite obvious that it must have varied very much in its nature. _Alumen nigrum_ was used to strike a black colour, and must therefore have contained iron. It was doubtless an impure native sulphate of iron, similar to many native productions of the same nature still met with in various parts of the world, but not employed; their use having been superseded by various artificial salts, more definite in their nature, and consequently more certain in their application, and at the same time cheaper and more abundant than the native.

The alumen employed as a mordant by the dyers, must have been a sulphate of alumina more or less pure; at least it must have been free from all sulphate of iron, which would have affected the colour of the cloth, and prevented the dyer from accomplishing his object.[97]

[97] “Quoniam inficiendis claro colore lanis candidum liquidumque utilissimum est, contraque fuscis et obscuris nigrum.”--_Plinii_, xxxv. 15.

What the _alumen rotundum_ was, is not easily conjectured. Dioscorides says, that it was sometimes made artificially; but that the artificial alumen rotundum was not much valued. The best, he says, was full of air-bubbles, nearly white, and of a very astringent taste. It had a slaty appearance, and was found in Egypt or the Island of Melos.

The _liquid alumen_ was limpid, milky, of an equal colour, free from hard concretions, and having a fiery shade of colour.[98] In its nature, it was similar to the alumen candidum; it must therefore have consisted chiefly, at least, of sulphate of alumina.

[98] See Dioscorides, lib. v. c. 123. Plinii Hist. Nat. xxxv. 18.

Bitumen and naphtha were known to the ancients, and used by them to give light instead of oil; they were employed also as external applications in cases of disease, and were considered as having the same virtues as sulphur. It is said, that the word translated _salt_ in the New Testament--“Ye are the salt of the earth: but if the salt have lost his savour, wherewith shall it be salted? It is henceforth good for nothing, but to be cast out, and to be trodden under foot of men”[99]--it is said, that the word salt in this passage refers to asphalt, or bitumen, which was used by the Jews in their sacrifices, and called _salt_ by them. But I have not been able to find satisfactory evidence of the truth of this opinion. It is obvious from the context, that the word translated _salt_ could not have had that meaning among the Jews; because salt never can be supposed to lose its savour. Bitumen, while liquid, has a strong taste and smell, which it loses gradually by exposure to the air, as it approaches more and more to a solid form.

[99] Matthew v. 13.--“Ὑμεις εστε το ἁλας της γης· εαν δε το ἁλας μωρανθη, εν τινι ἁλισθησεται· εις ουδεν ισχωει ετι ει μη βληθηναι εξω, και καταπατεισθαι ὑπο των ανθρωπων.”

Asphalt was one of the great constituents of the Greek fire. A great bed of it still existing in Albania, supplied the Greeks with this substance. Concerning the nature of the Greek fire, it is clear that many exaggerated and even fabulous statements have been published. The obvious intention of the Greeks being, probably, to make their invention as much dreaded as possible by their enemies. Nitre was undoubtedly one of the most important of its constituents; though no allusion whatever is ever made. We do not know when _nitrate of potash_, the nitre of the moderns, became known in Europe. It was discovered in the east; and was undoubtedly known in China and India before the commencement of the Christian era. The property of nitre, as a supporter of combustion, could not have remained long unknown after the discovery of the salt. The first person who threw a piece of it upon a red-hot coal would observe it. Accordingly we find that its use in fireworks was known very early in China and India; though its prodigious expansive power, by which it propels bullets with so great and destructive velocity, is a European invention, posterior to the time of Roger Bacon.

The word _nitre_ (רתנ) had been applied by the ancients to _carbonate of soda_, a production of Egypt, where it is still formed from sea-water, by some unknown process of nature in the marshes near Alexandria. This is evident, not merely from the account given of it by Dioscorides and Pliny; for the following passage, from the Old Testament, shows that it had the same meaning among the Jews: “As he that taketh away a garment in cold weather, is as vinegar upon nitre: so is he that singeth songs to a heavy heart.”[100] Vinegar poured upon saltpetre produces no sensible effect whatever, but when poured upon carbonate of soda, it occasions an _effervescence_. When saltpetre came to be imported to Europe, it was natural to give it the same name as that applied to carbonate of soda, to which both in taste and appearance it bore some faint resemblance. Saltpetre possessing much more striking properties than carbonate of soda much more attention was drawn to it, and it gradually fixed upon itself the term _nitre_, at first applied to a different salt. When this change of nomenclature took place does not appear; but it was completed before the time of Roger Bacon, who always applies the term _nitrum_ to our nitrate of potash and never to carbonate of soda.

[100] Proverbs xxv. 20.

In the preceding history of the chemical facts known to the ancients, I have taken no notice of a well-known story related of Cleopatra. This magnificent and profligate queen boasted to Antony that she would herself consume a million of sistertii at a supper. Antony smiled at the proposal, and doubted the possibility of her performing it. Next evening a magnificent entertainment was provided, at which Antony, as usual, was present, and expressed his opinion that the cost of the feast, magnificent as it was, fell far short of the sum specified by the queen. She requested him to defer computing till the dessert was finished. A vessel filled with vinegar was placed before her, in which she threw two pearls, the finest in the world, and which were valued at ten millions of sistertii; these pearls were dissolved by the vinegar,[101] and the liquid was immediately drunk by the queen. Thus she made good her boast, and destroyed the two finest pearls in the world.[102] This story, supposing it true, shows that Cleopatra was aware that vinegar has the property of dissolving pearls. But not that she knew the nature of these beautiful productions of nature. We now know that pearls consist essentially of carbonate of lime, and that the beauty is owing to the thin concentric laminæ, of which they are composed.

[101] “Cujus asperitas visque in tabem margeritas resolvit.”

[102] Plinii Hist. Nat. ix. 35.

Nor have I taken any notice of lime with which the ancients were well acquainted, and which they applied to most of the uses to which the moderns put it. Thus it constituted the base of the Roman mortar, which is known to have been excellent. They employed it also as a manure for the fields, as the moderns do. It was known to have a corrosive nature when taken internally; but was much employed by the ancients externally, and in various ways as an application to ulcers. Whether they knew its solubility in water does not appear; though, from the circumstance of its being used for making mortar, this fact could hardly escape them. These facts, though of great importance, could scarcely be applied to the rearing of a chemical structure, as the ancients could have no notion of the action of acids upon lime, or of the numerous salts which it is capable of forming. Phenomena which must have remained unknown till the discovery of the acids enabled experimenters to try their effects upon limestone and quicklime. Not even a conjecture appears in any ancient writer that I have looked into, about the difference between quicklime and limestone. This difference is so great that it must have been remarked by them, yet nobody seems ever to have thought of attempting to account for it. Even the method of burning or calcining lime is not described by Pliny; though there can be no doubt that the ancients were acquainted with it.

Nor have I taken any notice of leather or the method of tanning it. There are so many allusions to leather and its uses by the ancient poets and historians, that the acquaintance of the ancients with it is put out of doubt. But so far as I know, there is no description of the process of tanning in any ancient author whatever.