Part 50

_Assayer's weights, &c._ The materials used in assaying are accurately weighed in a balance of the most susceptible description; and the weights are given in terms of the 'notation' employed by assayers. The 'fineness,' 'richness,' or 'degree of purity' of gold is expressed in carats. Pure gold is spoken of as 24 carats fine; and any other sample containing in 24 parts only 12, 18, 22, &c., parts of pure gold, is said to be of as many carats fine. Every carat is nominally divided into 4 'assay-grains,' each assay-grain into 'quarters,' and each quarter into 'eighths' (= 1/32 carat), giving 768 "reports" for gold. On this system fractional alloys are commonly spoken of as of so many 'carats and thirty-seconds fine.' The real quantity taken for assay, technically termed the 'assay-pound,' is, however, very small, generally either 12 gr. or 6 gr., which makes each assayer's eighth-grain, or "report," equal to either the 1/64 or 1/128 gr. Troy, as the case may be. The nominal assayer's gold carat is 12 gr. The "journey-weight of gold" is 15 lbs. Troy (= 701 sovereigns = 1402 half-sovereigns).

The 'fineness,' 'richness,' or 'purity' of silver was formerly expressed in pennyweights; but is now generally reckoned in 1000ths, which admits of greater accuracy. Pure silver was said to be silver of 12 pennyweights." If it contained 1, 2, or 3 parts of alloy, it was termed "silver of 11, 10, or 9 pennyweights," as the case might be. Every assayer's pennyweight was nominally divided into 24 gr., and hence gave 288 fine grains, or 'reports,' for silver. The fineness of specimens containing odd grains was given in pennyweights and fine grains. The 'assay-pound' for silver, on this system, may be 24 Troy gr., when 2 real grains are equal to 1 'fine pennyweight,' and 1/12 real gr. equal to 1 'fine-grain.' In the decimal method pure silver is = 1000. The usual weight of silver taken for the 'assay-pound,' when the fineness is reckoned in 1000ths, is 20 Troy gr., every real grain of which represents 50/1000th of fineness; and so on of smaller divisions. The mint "journeyweight of silver" is 60 lbs. Troy (=3920 shillings, or a like value in other denominations).

_Ratio._ Cupellation, which is the distinctive and most important operation in assaying gold and silver, is founded upon the feeble affinity which these metals have for oxygen, in comparison with copper, tin, and other cheaper metals; and on the tendency which these latter metals have to oxidise rapidly in contact with lead at a high temperature, and to sink with it into any porous earthen vessel, in a thin, glassy or vitriform state. The conditions essential to the success of the process, and which are found in the precious metals, are--that "the metal from which we wish to part the oxides must not be volatile;" and that "it should also melt and form a button at the heat of cupellation; for otherwise it would continue disseminated, attached to the portion of oxide spread over the cupel, and incapable of being collected."[95]

[Footnote 95: Ure's 'Dict. of Arts, M., & M.,' 5th ed., i, 214.]

_Concluding Remarks._ The art of assaying requires very great care, skill, and experience, for its due exercise; and from the costliness of the precious metals, and their general employment for coin, jewelry, plate, &c., is of the utmost importance both to individuals and governments. Such is the extreme delicacy of the operation of cupellation that, without the requisites alluded to, it is more likely to fail than to give reliable results. An assay is thought to be good when the 'button' or 'bead' separates readily from the cupel, has a round form, with a brilliant upper surface, and the lower one granular and of a dead metallic lustre. When the upper surface is 'dead' and 'flat,' too much heat has been employed; and in the case of silver, some of the metal may have been lost by fuming or absorption. When the bead adheres to the cupel, or is spongy, variegated, or has scales of litharge still adhering to it, either too little heat has been used, or the process has been stopped before the assay was complete. The remedy is re-exposure to heat in the cupel, adding a little powdered charcoal or a few small pieces of paper, and continuing the heat until the metal 'brightens' and 'circulates' freely. The lead employed must be absolutely pure, or that technically called 'poor lead,' and, for this purpose, is commonly prepared by the reduction of refined litharge mixed with some carbonaceous matter, by heat; but, according to the late T. H. Henry, "lead reduced from the litharge of commerce usually contains from 10 to 15 _dwt._ of silver per ton." These remarks apply equally to gold and silver.

The process of assaying by the cupel, however skilfully conducted, gives much less accurate results, especially with silver, than the method of chemical analysis, often termed 'humid' or 'volumetrical assay,' whilst it is, in all cases, much more troublesome and expensive, and with compounds containing only small quantities of the precious metals, is not to be depended on. See GOLD, SILVER; also CARAT, CUPELLATION, PARTING, LIQUATION, QUARTATION, REFINING, &c. (and _below_).[96]

[Footnote 96: Those desirous of further information on the subject than that contained in this work, are referred to Mitchell's 'Manual of Assaying,' and to the various memoirs of Gay-Lussac, Chaudet, D'Arcet, Tillet, Brande, Ure, Henry, and others.]

=Assay of the Touch.= The fineness of JEWELRY, and of small quantities of GOLD which it is either impossible or inconvenient to assay according to the usual method, is generally determined by means of touch-needles and touch-stones. The former are made in sets, containing gold of different degrees of fineness, and differently alloyed with copper and silver. The latter are usually of black basalt; but pieces of good black pottery answer the purpose very well. The mode of using them is to mark the stone with the sample under examination, and to compare its appearance, hardness, colour, &c., with that produced by one or more of the needles. When the two are similar, the quality or 'fineness' is considered to be the same. The marks are then further examined by heating the 'touch-stone' to redness, and moistening the strokes with aquafortis, when the appearance resulting from oxidation, &c., differ according to the nature and quantity of the alloy. A nearly similar method is sometimes adopted with SILVER; but the characteristics are scarcely so distinct with the metal. (See _above_.)

=Hu'mid Assaying, Humid Assay.= Terms applied to the estimation of the quantity of gold and silver in ores and alloys in the moist way, more especially by the method known as volumetrical analysis. See GOLD (ESTIM.), SILVER (Estim.), VOLUMETRICAL ANALYSIS, &c.

=ASSIMILA'TION.= [Eng. Fr.] _Syn._ ASSIMILA'TIO, L.; ANEIGUNG, VERÄHNLICHUNG, &c., Ger. In _physiology_, the conversion of food into nutriment, and finally into the substances which compose the bodies of animals and plants; the function of nutrition.

=ASTHEN'IC.= _Syn._ ASTHEN'ICUS, L.; ASTHÉNIQUE, DÉBILE, Fr.; SCHWACH, Ger. Weak; debilitated. In _pathology_, an epithet of diseases (ASTHEN'IC DISEASES) accompanied by great and well-marked debility.

=ASTHEN'OPY.= _Syn._ ASTHENO'PIA, L. In _pathology_, incapacity to keep the eyes fixed on near or small objects for any length of time without confusion of vision. The common causes are over-exertion of the eyes, particularly by artificial light, or by a very brilliant one, or during convalescence; congestion of the ocular vessels; debilitating discharges or indulgences; and general nervous debility, however produced. It "appears to consist in weakness of the apparatus by which the eye is adjusted for the vision of near objects;" and along with this "there is an irritable state of the retina, connected in some manner with a tendency to internal congestion of the eyes."[97] The _treatment_ may consist of rest to the eyes, and ablution of them in cold water, with such other efforts to restore their tone and the general health as are noticed under AMAUROSIS. The prospect of complete cure, when the cause is not removable, is unfavorable; but even when confirmed the disease is not likely to end in blindness. The use of convex spectacles of very low power will generally be found serviceable. See EYE, SPECTACLES, VISION, &c.

[Footnote 97: T. W. Jones, 'Defects of Sight,' Lond., 1856; p. 82.]

=ASTH'MA= ([)a]st'm[)a][98]). [Eng., Ger., L., Gr.] _Syn._ ASTHME, Fr.; ENGBRÜSTIGKEIT, Ger. In _pathology_, a well-known disease coming on by fits, and characterised by shortness and difficulty of breathing, accompanied by a wheezing sound, cough, stricture and tightness of the chest, with other like symptoms. These gradually increase until the patient can no longer remain in a recumbent position, being, as it were, threatened with immediate suffocation; and they generally terminate, after the lapse of a few hours, in copious expectoration. The attack usually commences towards evening, and the symptoms increase in urgency during the night--often occurring suddenly after the first sleep--until at length, on the approach of morning, a remission takes place, and, in all probability, the patient, worn out and exhausted, falls into a sound sleep. On awaking in the morning he still feels the 'tightness' at the chest, breathes with some difficulty, which is increased by moving, and cannot lie in bed unless his head and shoulders are greatly raised. After a repetition of the fits for some nights, they at length moderate, and after more considerable remissions, pass off at last, leaving the patient in his usual state of health for a time, or until fresh exciting causes produce a return of the disease. For an evening or two previous to the fit the patient generally feels drowsy, indolent, and low-spirited, and experiences a sensation of fulness about the stomach, with headache, general uneasiness, and indigestion--these are the premonitory symptoms.

[Footnote 98: Asth'ma (with th fully sounded), as given by Knowles, is difficultly pronounceable, and is now obsolete.]

Asthma is principally confined to the later periods of life, and appears in many cases to be hereditary. It is generally severest in the heat of summer, or in the foggy or damp or windy weather of winter. The fits vary in duration from two to several hours. Sometimes copious expectoration commences early, which has led to the division of asthma, by nosologists, into two kinds--dry, nervous, or spasmodic asthma (ASTHMA SIC'CUM, L.) and humid a. (A. HU'MIDUM, L.).

The exciting causes of asthma are exposure to sudden changes of temperature, particularly from heat to cold; unwholesome effluvia, hard drinking, heavy meals, indigestion, violent exercise, and cold, damp, foggy, and sometimes windy weather.

_Treatm._ A dry, warm, and airy situation as a residence should, if possible, be sought. The use of flannel next the skin, and tepid or warm bathing is also advantageous. The bowels should be kept regular by mild aperients, and the stomach preserved in order by the adoption of a light and wholesome diet; particularly avoiding excess in either eating or drinking. The severity of the paroxysm may be generally lessened by adopting the sitting posture, and inhaling the vapour of hot water or of an infusion of chamomile. Small doses of camphor, ether, and opium, frequently repeated, may also be tried. The inhalation of the vapour of a little tar liquefied by heat is said to often produce considerable relief. The fumes arising from the slow combustion of porous paper dipped in a solution of nitre, and dried, have also been recommended. "The fumes of a piece as big as one's hand being placed on an earthenware plate, and ignited, presently become sensible throughout the room; and within a quarter of an hour their influence in many cases is rendered evident, in clearing the passages and gradually opening the air tubes." "Of calming vapours that of chloroform is, however, the one likely, in respect of its soothing power, to supersede all others. Inspired in moderate quantity, far less than is requisite to produce general insensibility, it has been found of singular efficacy in allaying, at once, the spasmodic distress of an asthma-fit. But it is a remedy too potent and subtle to be entrusted to the discretion of the patient himself." (Dr Watson); unless, indeed, he well understands its properties and nature, and has some friend near him to restrain his using it too freely--a thing he is, unfortunately, often tempted, by the urgency of the symptoms, to do. "Bleeding is an imprudent operation in every species of asthma" (Dr Bree); and has often proved highly injurious, especially in elderly persons. It is only in full plethoric habits, or when the paroxysms are very severe, and attended with signs of congestion of the lungs and brain, indicated by lividity of the countenance, stupor, extreme dyspn[oe]a, &c., that blood should be taken; and then only by 'cupping' between the shoulders, or by leeches to the chest. Emetics and active purgatives must also be avoided during the paroxysm; at which time costiveness may be best removed by an aperient clyster containing assaf[oe]tida. At other times, emetics (of ipecacuanha) and diaphoretics, followed by mild purgatives, may be administered with advantage; indeed, an emetic, taken a few hours before an impending fit, will frequently prevent its accession. Dyspeptic symptoms must be treated in the usual manner. "Chalk and opium will astonish the asthmatic, by the excellence of their effects when the irritation proceeds from dyspepsia of the first passages only." (Dr Bree.) The same authority also states that vinegar, separately administered, counteracts the flatulence and distension of the stomach.

Various other remedies have been recommended for asthma; among which are the smoking of tobacco and stramonium. In using the latter herb, the root and lower parts of the stem are chopped up and placed in the bowl of a common tobacco-pipe, and a few whiffs are occasionally taken. Drinking at the same time should be avoided. Lately _lobelia inflata_ (Indian tobacco) has been highly extolled in asthma, in doses of--tincture, 20 or 30 drops, to 2 teaspoonfuls--powder, 5 to 15 or 20 gr.; taken at the commencement or shortly before the accession of the fit, and repeated after the interval of an hour, if nausea or expectoration does not intervene. Sir John Floyer is said to have been cured of an asthma of 60 years' standing, at the age of 80, by the constant use of very strong coffee. Sir John Pringle adopted the same remedy with great success. He remarks, "One quality occurred to me which I have observed of that liquor (coffee), confirming what you have said of its sedative powers. It is the best abater of periodic asthma which I have seen. The coffee used ought to be the best Mocha, newly burnt, and made very strong immediately after grinding it. I commonly order an ounce for one dish, which is to be repeated with fresh coffee after the interval of a quarter or half an hour; and which I direct to be taken without milk or sugar."[99]

[Footnote 99: 'Letter to Dr Percival.']

Very recently cigars and cigarettes of _datura tatula_, Linn.--a peculiar species of stramonium--have been prepared by Messrs Savory and Moore; and are strongly recommended by Drs Watson, Latham, Fergusson, and many other physicians of eminence, as the very best remedy yet introduced for asthma.

A change of diet and habits, and particularly a change of residence, will often produce a marked improvement in asthmatic patients, and even effect a cure, when medicines have failed. The use of bark and bitters, or mild chalybeate tonics (when not contra-indicated), tends to improve the tone of the system, and may be adopted, in nearly all cases, with perfect safety. See BATH, AIR (Compressed), CIGARS, DATURA, &c.

_Treatment for Horses._ Ether and belladonna; chlorodyne; inhalation of chloroform; or amyl nitrite; subcutaneous injection of morphine or atropine; arsenic; and regular digestible diet.

=Asthma, Grind'er's.= See MELANOSIS.

=ASTHMA CURE.= 1. (Dr Aubrée, Ferte Vidame, Eure et Loire, France.) Decoction of senega (10 parts of the root), 250 parts; iodide of potassium, 50 parts; extract of opium, 4 parts; simple syrup, 500 parts; weak spirit, 200 parts. Coloured with some cochineal tincture. (Hager.)

According to a later analysis by Schröppel, this remedy is thus composed:--Iodide of potassium, 9 parts; French lactucarium, 1 part; water, 288 parts; simple syrup, 48 parts; chloric ether, 1-1/2 part.

2. (Kubale, Klitschdorf, near Bunzlau.) This is a solution of iodide of potassium, bromide of potassium, and sugar in water, strongly coloured with a cochineal tincture containing alum. It is supplied in six bottles, numbered 1 to 6, No. 1 being the weakest, and No. 6 the strongest in the iodide and bromide. In No. 3, for example, we found:--Iodide of potassium, 5 grms.; sugar, 2-1/2 grms.; alum, 1/3 grm.; cochineal colouring matter, 1/2 grm.; water, 200 grms. (Hager.)

=ASTHMA TEA= (Dr Orleïn). Recommended for difficulty of breathing, dry coughs, loss of sleep, loss of appetite, &c. Liquorice, 8 parts; marshmallow root, 6 parts; Iceland moss, 5 parts; a sort of buckbean, 2 parts; horehound, 2 parts. (Schädler and Selle.)

=ASTHMATIC PASTILLES= (S. Kittel's, now Daniel White & Co., New York). Set fire to the pastilles and inhale the smoke. An analysis found in 100 parts:--Nitrate of potash, 20·1 parts; impure resin of scammony, 3·5 parts; gum and sugar, 35· parts; charcoal, plant-stems, and leaves, 40·7 parts. (Dr Fleck.)

=ASTRIN'GENT= (-tr[)i]nje'-). [Eng., Fr.] _Syn._ ASTRIN'GENS, L.; ZUSAMMENZIEHEND, Ger. That straitens or causes wrinkling or constriction. In _pharmacology_, an epithet of substances or agents (ASTRIN'GENTS; ASTRINGEN'TIA, L.) which constrict animal fibre and coagulate albuminous fluids, and thereby obviate relaxation and check excessive secretion or discharges. In modern use, the word, both as an adj. and subst., is chiefly applied to internal remedies, those of a like character, employed externally, being usually termed 'styptics,' 'desiccants,' &c.

The principal astringents are--alcohol, alum, chalybeates (generally), sulphate of copper, sulphate and perchloride of iron, acetate and diacetate of lead, lime, bichloride of mercury, nitrate of silver, vegetable astringents (see _below_), acetate, carbonate, chloride, oxide, and sulphate of zinc, &c. See DESICCANTS, STYPTICS, TONICS, &c.

=Astringents, Min'eral.= See ASTRINGENT (_above_).

=Astringents, Veg'etable.= Of these the principal are--alkanet, bistort, catechu, the cinchona barks and their alkaloids, dragon's blood, French or red rose, galls, kino, logwood, mastiche, oak-bark, red sanders wood, rhatany, tormentil, tannic acid, gallic acid, and areca nut. (See _above_.)

=Astringent Prin'ciple.= A term formerly restricted to tannin; but now commonly applied to the astringent matter of any vegetable.

=ATMOM'ETER.= _Syn._ ATMIDOM'ETER; ATMOM'ETRUM, &c., L.; ATMOMÈTRE, &c., Fr. In _chemistry_ and _meteorology_, an instrument for measuring the rate of evaporation from a humid surface. It is of very simple construction, and possesses some practical value. It consists of a long glass graduated tube divided into inches, having attached to the bottom a hollow ball made of porous earthenware, similar to that used in water bottles. When used, water is poured in at the top until it rises to the zero point of the scale. The outside of the porous ball being always covered with dew, the more rapidly the evaporation takes place, the more quickly will the water fall in the tube.

=AT'MOSPHERE= (-f[=e]re). _Syn._ ATMOSPHE''RA, L.; ATMOSPHÈRE, Fr.; ATMOSPHÄRE, DUNSTKREIS, Ger. Primarily, a 'vapour-sphere,' appr., the assemblage of respirable gas and aëriform vapours which surround the earth; fig., any surrounding medium or influence.

_Comp., Chem. prop., Pur., Uses, &c._ See AIR (Atmospheric).

_Mechanical properties_ of the atmosphere:--

COLOUR:--The prevailing colour of the atmosphere is blue; at considerable elevations this blue tint is lost, and the sky appears deep black. The prevalence of blue is referred to the greater facility with which the blue and violet rays are reflected, whilst the glowing tints of morning and evening are conceived to arise from the red rays possessing greater momentum than the other rays of the spectrum.

DENSITY:--The density of the atmosphere diminishes with the distance from the earth's surface, and this is the duplicate ratio of the altitude. Thus, if at a given altitude the density of the air is only one half what it is at the level of the sea, at twice that elevation it possesses only one fourth that density. On this fact depends the application of the barometer to the determination of the elevation or depression of any point above or below the level of the sea, taken as a standard.

_Density of the Atmosphere at Different Elevations._ By Prof. GRAHAM.

+----------------------+-------+-------------+ |Height above the level|Volume |Height of the| | of the Sea in miles. |of Air.| Barometer. | +----------------------+-------+-------------+ | 0· | 1 | 30 | | 2·705 | 2 | 15 | | 5·41 | 4 | 7·5 | | 8·115 | 8 | 3·75 | | 10·82 | 16 | 1·875 | | 13·525 | 32 | ·9375 | | 16·23 | 64 | ·46875| +----------------------+-------+-------------+

HEIGHT, &c.:--If the density of the air were uniform throughout its whole extent, the height of the atmosphere, measured by a corresponding column of mercury, would be barely 5-1/4 miles. As, however, its density decreases with the distance from the earth's surface, its real height must be considerably greater. Kepler found that the reflection and refraction of the sun's rays by the atmosphere, producing twilight, ceases when that luminary descends 18 degrees below the horizon, whence it is calculated that the atmosphere cannot have a greater altitude than 45 miles. On the other hand, there is reason to believe that it cannot be much less than this sum. "With a good air-pump air may be rarefied 300 times; supposing this to be the utmost limit to which rarefaction can be carried, the atmosphere would still extend to an altitude of above 40 miles." Whether, in a state of extreme tenuity in which its grosser properties are lost, it extends indefinitely into space, was formerly a subject of controversy. That its boundaries are limited, and that it belongs exclusively to our earth appears almost certain. "We are warranted in concluding that the atoms of air are not infinitely divisible, and consequently that the atmosphere has a limit; and the limit must be situated at that height above the earth where the gravitation of the atoms is just equal to the force of their repulsion."[100] Under ordinary circumstances the mercury of the barometer falls about one inch for every 1000 feet of elevation.

[Footnote 100: Brande's 'Dict. of Lit., Sci., & Art.']