May 13, 1892.] 



SCIENCE. 



277 



not even as great as that of feldspar, never that of quartz. Popu- 

 lar beliefs are not scientific facts, and it is a scientiflc fact that 

 nothing but the natural edge of a diamond crystal will cut glass 

 (frequently with vei-y httle visible scratching), but everything 

 having the hardness of feldspar will scratch it, as well as glass 

 itself. Popular errors are numerous, and these errors are fre- 

 quently extensively copied. For instance, a statement appeared 

 some years ago in one of our large magazines that if a precious 

 stone could not be scratched by quartz it would surely be a dia- 

 mond, and that any jeweller who would object to having a 

 diamond tried with a file should be condemned as a fraud. 



Polishing the surface of a precious stone can in no way affect 

 its specific gravity if the stone is properly cleaned, and if the 

 operator has a delicate balance and sufiBcient experience. In these 

 circumstances it is surprising what exact results the various colors 

 of the various precious stones give us. Further, I may say that, 

 after visiting nearly all the known gem-cutting centres and the 

 chief seats of the manufacture of imitation gems, I have never 

 yet known of an instance where the manufacturer cared the 

 slightest what the specific gravity of his product was, providing it 

 had the desired color, or, if it were to imitate a diamond, it had a 

 greater amount of brilliancy than the material made by one of his 

 most successful competitors. The majority neither know nor care 

 what the specific gravity of the gems is any more than does the 

 regular jeweller. 



As regards the optical properties of gems no mention is made 

 of the dichroscope, with the use of which the facetting in no way 

 interferes. The polariscope is also of considerable value. In 

 fact, in the determination of rubies, sapphires, and emeralds, 

 their pronounced optical properties, as shown by the dichroscope, 

 or the polariscope and the spectroscope, together with their specific 

 gravity and their hardness, which is so much greater than that of 

 quartz, will readily distinguish them from everything "imitation." 

 By means of the spectroscope we obtain the red band for the ruby, 

 the absorption bands for the garnet, at D, E, and F in the spec- 

 trum, or the series of black absorption bands for the zircon. To 

 distinguish glass from a real ruby requires but a glance ; to detect 

 the difference between rubies, spinels, garnets, and rubellite is not 

 80 easy, and in these cases fusibility is of no value. 



I think the experience of those who have given attention to this 

 matter is. first, that the specific gravity of the various precious 

 stones is remarkably constant according to their color, seldom 

 varying more than one in the second place of decimals, and, sec- 

 ond, that the hardness of the gem is also remarkably constant, 

 and that lines can be more clearly drawn in cut than in natural 

 crystals, which are frequently not transparent, owing to impuri- 

 ties; namely, placing the sapphire at 9, the ruby at 8 8. the aqua- 

 marine at 8, and the emerald at 7.8. 



I should not want to be responsible for the consequences if, 

 at a jeweller's, anyone tried heating a gem in the flame of a spirit 

 lamp or in the flame of a Bunsen burner, any more than I should 

 if a buyer started to try a diamond with a flle. Nor should I care 

 to be responsible for the heating in a Bunsen burner of a fine ruby 

 or sapphire, which frequently contains fluid-cavities, or of an 

 emerald, which, if of a fine color, is seldom perfect, owing to in- 

 ternal striae and fluid-cavities, or the topaz, which is affected by 

 heat, and nearly always contains many minute fluid-cavities. The 

 fusibiUty of the edges of the gems would not distiufjuish the arti- 

 ficial rubies of Fremy from those of the true ruby, as both are in- 

 fusible. Nor would the test of heating in a Bunsen burner be 

 practicable if Mr. Miller were called upon to examine in a few 

 hours from one thousand to fifty thousand gems, and at the same 

 time be perfectly sure that there were no imitation gems in the 

 lot. Such testing needs the experience of the expert, who, before 

 he opens a paper marked " blue or green aquamarine," can tell 

 simply by the weight that the stone in the paper is a blue or green 

 topaz, or who, if the stone is labelled "yellow topaz," can, with- 

 out looking at it, but simply by the facility with which it slips 

 through the fingers, determine that it is citrine (decolored smoky 

 quartz) or the true mineral topaz; or who, if one hundred stones 

 mounted as rings were placed before him in a tray, without sup- 

 posing the presence of an imitation stone, could at once detect the 

 single imitation present. Nor would fusibility be of any value in 



the examination of that class of imitations which are made by 

 dipping heated quartz in green, red, or blue solutions, a common 

 variety of which is known as Mount Blanc, or Alpine ruby. 



Finally, few mountings which secure gems are improved by 

 heating them to any extent, and generally the owners do not wish 

 the settings disturbed. As to imitation diamonds there is surely 

 not a jeweller worthy the name who cannot tell a true diamond 

 from a paste one at the first glance, by its adamantine lustre. If 

 it scratches sapphire he may be sure it is a diamond, whereas 

 putting the gem into the flame would not distinguish the diamond 

 from the white topaz or the white zircon or the white sapphire or 

 the white tourmaline or any other white stone that is not fusible. 



In conclusion, let me suggest to Mr. Miller the simple test for 

 diamonds, of drawing the stone sharply over a piece of unpainted 

 board in a dark room. Every diamond phosphoresces by friction. 



George F. Ktjnz. 



New York, May 11. 



Artificial Production of Variation in Types. 



In reply to your request for a few words on the question of arti- 

 ficial production of variations, as presented by Mr. West in Science 

 of April 32. I may say that I quite agree with Mr. West in think- 

 ing that all attempts to produce new species by mutilations of the 

 parents are foredoomed to failure. The idea that the embryo is 

 in any sense a reflected image of the parent, and consequently that 

 any particular loss or modification of an organ in the parent dur- 

 ing adult life must impress itself upon the embryo, has not a 

 shadow of a basis in embryology. 



Mr. West asks, ' ' Would it not seem the proper and only 

 method to study the laws governing the modifications of the em- 

 bryo?" If we substitute germ-cells for ''embryo," the question 

 may be answered affirmatively. If the question, as it stands, im- 

 plies that modifications received during embryonic life,as the result 

 of external influences, would be any more likely to repeat them- 

 selves in the next generation than if acquired during adult life, I 

 should say that the assumption is entirely unwarranted. 



The form and features of the adult are predetermined in the 

 constitution of the germ-cell. No one denies that external condi- 

 tions and influences may affect more or less the course of develop- 

 ment ; but the speciflc form of the adult is already settled in the 

 germ before development begins. These are mere truisms in em- 

 bryology. C. O. Whitman. 



Clark University, Worcester, Mass. 



The " Hongote '' Language. 



In a series of ten studies of South American Languages, princi- 

 pally from MS. sources, which I published in the last num- 

 ber of the Proceetjings of the American Philosophical Society, 

 one was partly devoted to the " Hongote" language, a vocabulary 

 of which I found in a mass of documents in the British Museum 

 stated to relate to Patagonia. I spoke of it as an independent 

 stock, not related to other languages of that locality. In a letter 

 just received from Dr. Franz Boas, he points out to me that this 

 ' ' Hongote " is certainly Salish, and must have been collected in 

 the Straits of Fuca, on the north-west coast. How it came to be 

 in the MSS. referred to, I cannot imagine, but I hasten to an- 

 nounce the correction as promptly as possible. 



D. G. Beinton, M.D. 

 Philaaelphia, May 4. 



AMONG THE PUBLISELERS. 



The number of the American Journal of Psychology which is 

 about to appear will contain an article on the variations of the 

 knee-jerk by Dr. Noyes, which contains the results of experiments 

 on a case of dementia. Mr. Bolton contributes a digest of the ex- 

 periments on memory made by Dr. Boas in the Worcester schools. 

 Mr. Eraser shows the psychological origin of the naive realism of 

 the unthinking man and of the philosophic realism of the Scottish 

 school ; both are due to a postulate of the sensations of touch as 

 the ultimate realities. The old philosophers have before this 



