Part 2

The most interesting thing about the giraffe is the okapi. The remark sounds absurd, but it is true. The okapi is the new animal from the Congo forest of Central Africa, discovered in 1901 by Sir Harry Johnston. It is as big as a very large stag, has a neck like a deer, and is striped on the haunches and legs, not spotted as is the giraffe. Yet its teeth and its horns prove it to be a close ally, not of deer, but of the giraffe. Any points of agreement between giraffes and the okapi are, therefore, important. I have examined the baby giraffe at the Zoo, and find that she has stripe-like bands of hair on the face and on other parts of the head. Both her father and mother are from Kordofan, and have some six or seven strongly-marked bands of dark hair over the eyes and on the muzzle. It is important to note any colour-striping in the giraffe’s skin, since the giraffe’s colour-markings are mostly in the form of great spots, whilst the okapi is only marked by stripes or bands something like those of a zebra, but confined to the haunches and the legs, the rest of the body being dark brown. The tendency to develop colour stripes in the giraffe is important, since it shows us that the stripes do not separate the okapi absolutely from the camelopard; they are a common possession or possibility of the two animals. It was my examination of a half-brother of the little giraffe now alive at the Gardens which led to the discovery of striping on the head and face of giraffes. The mother in that case had died before the birth of her young one, and the dead calf was given to me by the secretary of the Zoological Society. Sixty-eight years ago Sir Richard (then Professor) Owen received a new-born giraffe from the Gardens, and reported on it to the Zoological Society. No one had examined one since that date; none were obtainable from the Zoo, and I could get none from African travellers and sportsmen, in spite of urgent requests. I was accordingly greatly pleased to secure one from the London Gardens. A great peculiarity of the young giraffe is that it is born with a pair of well-grown horns, nearly an inch long, and covered with coarse black hair. No other horn-bearing mammal--no antelope, buffalo, ox, sheep, goat, stag, or other deer--is born with horns, so far as we know, and we know a good many of these animals well. Before birth the young giraffe’s horns are flat from back to front, and quite soft and flexible. They can be pressed backwards, so as to be made to lie flat on the head. Directly after birth a hard, bony deposit commences inside the horn, and after some years’ growth it becomes firmly fused to the skull. But the hard bony core never breaks through the hairy skin which covers it. The bony core of the okapi’s pair of horns, on the contrary, does “cut” or break through the skin, exposing a sharp, hard point, a quarter of an inch in length. In the deer tribe, as everyone knows, the point of the bony horn-core spreads out as a large, branching growth from which all covering is shed, and forms the “antler.” The deer tribe shed the antlers every year from the top of the horn-core, and grow a new and larger pair to take the place of the old ones. Moreover, in them the horn-core itself is a stem-like upgrowth of the bone of the skull (of the frontal bone). In the okapi and the giraffe the horn-core is a separate bone, free at first and fusing with the skull only when the adult condition is reached. The little antlers or bare-points of the okapi’s horn-cones or cores seem to be shed in segments as growth goes on, and are only minute things compared with the antlers of stags. The giraffe’s horns, on the other hand, always remain covered by skin and hair and have a broad, rounded top, not a sharp point.

The real clinching feature in the okapi and giraffe which decides at once their close affinity to one another is found in the outer tooth on each side of the group of eight teeth placed in the front of the lower jaw. In both this particular tooth has a broad, chisel-like crown, divided into two portions by a deep vertical slit. None of the other ungulate or hoofed animals have this very curious shape of tooth. It is a sort of family “mark” or “feature” in okapis and giraffes, as may be seen in specimens shown in the gallery of the Natural History Museum, where we have now no less than three fine, well-stuffed okapis and several varieties of giraffe.

7. _The Great Geologists of Last Century_

The centenary of the foundation of the Geological Society of London, celebrated last year, was a genuine festival in the scientific world. Though geology had its teachers and searchers before 1807 (Hutton and Werner, and the Neptunian and Plutonic schools, with their theories as to the origin of rocks on the one hand by marine deposit, or on the other by igneous agency, flourished before that date), yet it is true that the adequate conception of the problems of geology and the proper use of accurate observations and of judicious theory based on those observations, in relation to the problems of geology, coincided with the foundation of the society. It was not the first “special” scientific society founded in London; there was already the Linnean Society (founded in 1788) for the cultivation of zoology and botany. Yet it incurred the displeasure of the worthy president of the Royal Society, Sir Joseph Banks, who at first joined it, and then withdrew from it, when, in 1809, it ceased to be a dining-club, meeting at a London tavern, and acquired rooms of its own at No. 4, Garden-court, Temple. Apparently there was a notion in those days that the “Royal Society for the promotion of Natural Knowledge,” founded in 1662, should exercise a sort of paternal control over any society formed for the special promotion of one branch of science. Independence has, however, been found to be the healthiest condition, and we now have not only the Linnean and the Geological, but the Zoological, the Chemical, and the Physical Societies, vigorous and important corporations, publishing their “Transactions,” and meeting for discussion. There is, it is true, a danger that the Royal Society may be left eventually, owing to these independent establishments, in the sole possession and control of the doctors and the engineers. It is a curious fact that the word “physiology,” which in Cicero’s time (he says “Physiologia naturæ ratio”) and in the Middle Ages meant what we now call “natural history,” has been abandoned by other sciences, and appropriated by the medical men. In England, but not abroad, the doctors have even usurped the words “physician” and “physic.” In France, on the contrary, and more correctly, Lord Rayleigh and Sir William Crooks are called distinguished “physicians,” and the theory of the luminiferous ether is “physic.”

The Geological Society issued its first volume of Transactions in 1811. The origin of the society is there stated to be due to “the desire of its founders to communicate to each other the results of their observations, and to examine how far the opinions maintained by the writers on geology are in conformity with the facts presented by nature.” A more exact and intelligible statement of the attitude of scientific men, then and now, could not be formulated.

There are few, if any, among us now who knew many of the original members of the Geological Society, but I remember meeting, when I was a youth, Leonard Horner, the first secretary of the society, and father-in-law of Sir Charles Lyell. I also knew Dr. Peter Mark Roget, an original member, who was the oldest fellow of the Royal Society when he died in 1869. Sir Henry Holland, the father of the present Lord Knutsford, became a member in 1809, and published a paper on the rock-salt district in the first volume. He was an eminent medical man, and a great traveller. He wrote, amongst other things, upon the turquoise mines of Persia and upon longevity. He was a friend of my father’s, and I had the advantage of talking the latter subject over with him before I wrote a little book on “Comparative Longevity” in 1869.

It was not until 1825 that the Geological Society obtained a charter, and was incorporated. Two great names appear in the first council of the newly-incorporated society--Murchison and Lyell. Murchison became the Director of the Geological Survey, and as “Sir Roderick” was a familiar and picturesque figure in the scientific world of the second and third quarters of last century. He wore an Inverness cape and a tall hat with a large and much-curled brim, an old-fashioned stock, and a tail-coat. In his hand he always grasped a large, handsome cane, with which he expressed his applause during the discussions at the society, or emphasised his own remarks. He was fond of alluding to himself as “an old soldier of the hammer,” and almost always entered into a discussion with these words, “It is now, sir, a quarter of a century since, in company with my illustrious friend, Sir Somebody Something, I had the privilege and pleasure of showing that”--whatever it might be. Discussions at the Geological in the sixties and seventies were real, animated, almost violent discussions. I need hardly say that they were perfectly delightful. Godwin Austen was a fine, incisive speaker, who seemed ready to back his statements and views with his fists, if need be. Lyell, the greatest of all, was most modest, and almost timid in pressing an opinion, but full of personal experience and minute knowledge of facts. John Phillips, the nephew of the father of English geology, William Smith, was mellifluous and persuasive; Jukes, robust and defiant; Huxley (secretary and then president), clear, trenchant, and uncompromising. I remember an occasion when Sir Roderick, with tears in his voice, if not in his eyes, declared he would not stay in the room to hear that fossil fishes were discovered in his own special domain--the Silurian rocks, where he had long since shown that they did not occur--and he left the meeting. Many Silurian fishes have now been found, but we all loved Sir Roderick for the heart and feeling which he threw into his work and his public utterances.

The aim of geology is to describe accurately the long succession of changes in the crust of “this cooling cinder,” the earth, and to assign them in an orderly way to their causes. Hence, it calls upon nearly all other branches of science for help--astronomy, physics, chemistry, mineralogy, botany, and zoology. At the same time, it is essentially a recreative pursuit, for, as Mr. Horace Woodward says in his _History of the Geological Society of London_--published by the society--“the fulness of the science can never be attained without the vivifying influence of mountain and moor, of valley and sea coast.” It is owing to this that the soldiers of the hammer, from Murchison, Sedgwick, Lyell, Ramsay, Etheridge, Salter, onwards to the present generation of “stone-crackers,” are amongst the happiest, most genial, and mentally alert of our men of science.

That word “stone-cracker” I take from a letter addressed to me when I was a boy of twelve by the Rev. J. S. Henslow, Professor of Mineralogy and later of Botany at Cambridge, founder, with Adam Sedgwick, the great Woodwardian Professor of Geology, of the now flourishing Cambridge Philosophical Society, and the teacher, guide, and fateful friend of Charles Darwin. It was he who sent Darwin on the voyage of the _Beagle_. I had met this wonderful old naturalist at Felixstowe when exploring the marshes for rare plants and insects with my father. My father was a first-rate man at a country walk, and could tell you all the time about the flowers, flies, stones, and bones you might encounter. But Henslow surpassed him. I remember to this day nearly every word Henslow said, and everything he did on that memorable afternoon nearly fifty years ago. Amongst other things he explained how the rough flint implements recently discovered in river gravels--proving man’s great antiquity--could be shown to owe their shape to blows, each blow causing a “conchoidal” fracture. And he struck with his hammer some very large flints which were lying in a heap in the meadow, and produced the most perfect dome-like broken surface or bulb of percussion. He promised to give me a real palæolithic flint implement and also a geological hammer. The letter which reached me later in London ran as follows: “Dear incipient Stonecracker--Enclosed you will find a draft for 10_s._ with which, at the shop in Newgate-street, you can obtain a geological hammer identical in all respects with my own.... In a separate parcel I send you a flint implement which I obtained myself in the gravel pit at St. Acheuil....” The hammer, the flint-axe, and the letter are to this day treasured with deep affection and reverence for the giver, by the boy who was thus so kindly initiated in the “art and mystery” of Stone-crackers. Henslow died in 1861 at the age of 65. His daughter was the first wife of Sir Joseph Hooker, the great botanist and traveller, who celebrated his ninetieth birthday in July, 1907, and is still in full mental and bodily health and vigour.

8. _Experiments with Precious Stones_

A man of science cannot say a word about experiments with precious stones nowadays, but he is liable to be misunderstood and represented as having discovered how to make valuable gems out of dirt, or of enormous size, and in vast quantity. Last year the production of a few small crystals by the electrical decomposition of bisulphide of carbon was announced as something to affect the stock market instead of as a matter of interest to a few learned chemists. The crystals were supposed--erroneously as it turned out--to be diamond. We were also gravely told that a competent French chemist had discovered, and that the distinguished geologist, Professor Lapparent, had communicated the fact to the Academy of Sciences, that the radiation of radium acting on “corindon,” or, as we should prefer to write it in England, “corundum”--a base, dull, colourless crystal--converts that dull substance into sapphires, rubies, emeralds, and topazes--and that the dealers attest the value of the precious stones so produced. This is really great nonsense, and arises from a little confusion in the use of the names of precious stones, and ignorance of what the substances indicated by those names are--defects which we cannot attribute to the French chemist, but must suppose to have “crept in” to the reports which crossed the Channel. Corundum is a colourless crystal, opaque or translucent. In chemical composition it is the oxide of aluminium--standing in the same relation to that light, white metal as rust or hematite ore does to the metal iron. It would not be at all astounding if by simple treatment we could convert corundum into sapphire or into ruby, since sapphire and ruby have precisely the same chemical constitution as corundum--are, in fact, only coloured varieties of corundum. Sapphire is blue, transparent corundum; green and yellow “sapphires” are also common. The Oriental ruby is similarly only red, transparent corundum--like it only oxide of aluminium or alumina.

Diamonds are pure crystalline transparent carbon. Commonly they are colourless and transparent, but are sometimes black or white and opaque. Transparent diamonds are often found of a straw colour, rarely of a deep blue (the Hope Diamond), more rarely green (the Dresden Diamond), and rarest of all red.

If radium were really able (as some people have wrongly inferred from the French experiments) to change the chemical nature of corundum and convert it into topaz and emerald, the case would be very different from that of merely changing the colour of the corundum. What is to-day called “topaz” is a sherry-yellow crystal consisting of silicate of alumina and of fluoride of alumina. It turns pink when heated, and is also known of a blue colour and colourless. The topaz of the ancients from the coasts of the Red Sea is of a different chemical nature, and is now called peridot. Yellow corundum is sometimes wrongly called Oriental topaz, and the yellow-brown quartz crystals properly known as cairngorms are sometimes wrongly called Scotch topaz. So that the word “topaz” is used loosely as well as strictly, and confusion results. Emerald is widely distinct from corundum, sapphire, and ruby. It is a silicate of alumina and beryllium, and in its coarse and pale-coloured variety is known as beryl.

From all this it appears that some names of precious stones indicate substances quite distinct from one another chemically, built of differing elements, and also _per contra_ that what is actually one and the same kind of precious stone in chemical composition and native crystalline form may present examples possessing various colours and degrees of transparency, each variety being called by a distinct name, and regarded popularly as a distinct kind of stone. Radium rays can convert colourless alumina or corundum into blue alumina (sapphire) or red alumina (ruby), but they cannot change alumina into beryllia (that is into emerald), nor into fluoride (that is into topaz).

One naturally asks, “To what is the colour of these precious stones due?” The answer is difficult, because very minute traces of chemical impurity, such as iron, cobalt, manganese, or chromium may suffice to tint an otherwise transparent, colourless crystal with the brightest red, yellow, blue, violet, or green. Moreover, it is certain from what we know of traces of metallic impurity in artificial glass that it may exist in such a state of chemical combination as to give no tint whatever to the glass, but after prolonged exposure to light or other agencies, the minute impurity may combine chemically with oxygen present in the glass and develop colour. Thus, for instance, old window-glass often assumes a violet or amethystine tint after long exposure. This varying colour of the combinations of metals according to whether they are oxidised or not, and the degree of oxidation, or the special salt which they may form, is in itself an unexpected thing to those who are not chemists. The metal chromium, for instance, gives rise to colourless, to yellow, red, green, and blue combinations. Manganese, a metal commonly associated with iron, gives rise to brilliant green, to violet, and to wine-red combinations, and if scattered as microscopic particles of black oxide in glass would produce no colour effect at all. From what we know of glass and the ease with which it is coloured to every shade of the rainbow by the admixture of traces of metallic impurities--so that “paste” or glass gems of all colours can be manufactured--it is not surprising to find that natural crystals, transparent and often devoid of colour (such as corundum, diamond, quartz, and topaz), are yet also found more or less frequently coloured in various tints. Nevertheless, it is the fact that in very few cases have chemists been able to prove by analysis what precisely is the cause of the colour in any given crystal or precious stone, although they may strongly suspect this or that as the colour-giving impurity. The actual quantity of a metallic impurity sufficient to give a tint is so excessively minute that the chemist finds it impossible to determine what it is by examining one small precious stone. He has not a sufficient bulk of material to operate on.

Having reached this point, we can see that such potent disturbing agents as the rays of radium--penetrating a colourless, or faintly-coloured, crystal--may determine oxidation or other chemical combination within the crystal of traces of metal (iron, cobalt, manganese, chromium) already present there, and so give it an increased colour or an altogether new tint. In 1905 (therefore long before the recent French experiments had shown that the radium rays will act in this way on corundum, the “base variety” of sapphire and ruby), Sir William Crookes published an account of his experiments as to the action of the radium rays on the diamond. “Some fine colourless crystals of diamond,” writes Sir William Crookes in 1905, “were embedded in radium bromide, and kept undisturbed for more than twelve months. At the end of that time they were examined. The radium had caused them to assume a beautiful bluish-green colour, and their value as ‘fancy stones’ had been materially increased.” On another occasion Sir William found that a yellowish “off colour” diamond had its tint changed to a pale blue-green when embedded for six weeks in a tube with radium bromide. (I have seen this stone.) He also has succeeded in improving the clearness of diamonds by exposing them to radium rays. Everyone who has experimented with radium knows that it causes the glass which may be used to keep it covered to develop a brown or purple tint. This, then, is the explanation of the results obtained by the French observer with corundum, as reported a few months ago. There was no “transformation” of one substance into another, nor did he himself suggest that there was. The radium rays merely acted chemically on minute impurities present in colourless or pale-coloured crystals, and so produced colour as they do in diamonds or in glass.

9. _Diamonds_

His Majesty King Edward was presented with the great Cullinan diamond from the Transvaal in November 1907. This diamond weighs one pound and one-third (avoirdupois)--more than 21 oz. I have placed a good glass model of it in the Central Hall of the Natural History Museum; in the case with it is a glass model of another big diamond, the “Excelsior,” as now cut, and also models of the “Pitt” diamond, in the rough and in the cut condition. Diamonds lose enormously in the process of cutting. The Excelsior, like the Cullinan, is a Cape diamond of fine quality, and free from colour. It was the biggest diamond known until the giant Cullinan was found: in the rough it weighed 7 oz., or less than a third of the Cullinan. As now cut, it only weighs 1-3/4 oz. It is reduced to a quarter of its original size.

In the same way, the Pitt diamond, an Indian one, named after General Pitt, of Madras, weighed originally 3 oz., and is now (it is in Paris, in the Louvre, and is called “The Regent”) less than an ounce in weight. The biggest Indian diamond known--the Nizam--is not quite twice this size, whilst the Kohinoor, which is probably a fragment (a third) of the “Great Mogul”--a diamond which has disappeared, leaving only tradition and surmises as to its history--weighs no more than three-quarters of an ounce. This seems a small affair by the side of the twenty-one ounces of the Cullinan.

No one can guess what will happen to the Cullinan in cutting it. At the best, it may be reduced to something between four and five ounces in weight, and it may “fly” into fragments. It would be necessary deliberately to cut it up into smaller stones in order to obtain the full result of flashing of light and colour which twenty-one ounces of diamond can produce. And the operation of cutting and polishing is enormously expensive. One would have hoped that Sir William Crookes and other men of science would have been asked to examine this wonderful mass of transparent carbon by means of polarised light, Röntgen rays, and radium, and to determine exactly its specific gravity before it was broken up. Indeed, it would probably have retained its greatest interest and value if never cut at all.