1 84 



SCIENTIFIC NEAVS. 



[Feb. 24, iS 



mates more closely to their apparent brilliancy, thus 

 rendering it easier to identify the stars depicted on the 

 diagrams. With the aid of this excellent and cheap 

 little work, teachers in public elementary schools should 

 be able to give their pupils enough instruction to enable 

 them to take an intelligent interest in the appearance of 

 the heavens. 



The Cotistellations and How to Find them. A Popular and 



Simple Guide io a Knowledge of the Stany Heavens. 



By William Peck, F.R. A.S. London and Edinburgh : 



Gall and Inglis. Fourth Edition. 



This work is illustrated with thirteen maps, showing 



*he position of the constellations in the sky during each 



month of any year, with a separate description of each 



map, and the fact that this work has reached its fourth 



■edition shews that it is evidently appreciated. The only 



fault we have to find with it is that the stars of the first 



magnitude are a little too strongly marked. Small 



figures are given in the text showing the position of the 



stars which have blazed out in the Crown, the Swan, 



and in Cassiopeia. The expected reappearance of the 



latter gave rise to the recent craze about the Star of 



Bethlehem. 



Exercises in Quantitative Chemical Analysis. By W. 



Dittmar, LL.D., F.R.S. Glasgow : Hodge and Co., 



1887. 

 The man who does not find himself an accurate and 

 capable analyst after honestly working through Professor 

 Dittmar's Exercises, may fairly conclude that he has 

 mistaken his vocation. The drilling it gives is so thorough, 

 the attention to practical details so minutely careful, the 

 theory so sound, that the presumption would be almost 

 a certainty. In addition to exercises in the analysis of 

 inorganic and organic compounds and mixtures, there is 

 an admirable chapter on gas analysis, in regard to which 

 every embryo chemist has felt the difficulty of getting 

 reliable information. The book has many illustrations 

 of apparatus ; and last, but not least, a good index. We 

 <;an confidently recommend it to those of our readers who 

 are studying quantitative chemical analysis, as likely to 

 correct their special faults, and form in them those habits 

 of exactness and orderliness which are essential for every 

 good chemist. 



Journal of Morphology. Edited by C. O. Whitman. Vol. 



I., No. I, September, 1887. Boston : Ginn and Co. 



London : W. P. Collins, 157, Great Portland-street. 

 This journal is chiefly devoted to embryological, 

 anatomical, and histological subjects, more especially in 

 reference to animals rather than to vegetables. The 

 first volume now before us contains articles on Sphryce- 

 Mura Osleri, on the Development of the Compound Eyes of 

 Crangon, on the Germ-bands of Lumbncus, and on other 

 interesting biological subjects. There is an interesting 

 article on the Phylogenetic Arrangementof the&«ro/s/'(f(7, 

 wherein Professor Baur, who in 18S6 published evidence 

 showing that the fossil Stereosternmn tumidmn from the 

 carboniferous strata of Brazil, which Cope described as 

 Batrachian, is really a reptile allied to the Rhynchocephalia, 

 points out the advisability of forming a new order of 

 reptiles which may contain Stereosternmn. For this new 

 order he proposes the name Proganoiauria, and he looks 

 upon it as the genetic source of the other reptiles. 



The lithographic plates are exceptionally good, and a 

 very fine feature in the journal. 



MANUFACTURE AND COLORATION OF 

 PRECIOUS STONES. 



PRECIOUS and semi-precious stones are the subject 

 of no little manipulation before they reach the 

 purchaser. We do not here, of course, refer to those 

 fraudulent imitations of jewels which are now manufac- 

 tured on a considerable scale, and which not only figure 

 in cheap rings, bracelets, and other personal decorations, 

 but are too often palmed upon the unwary as genuine. 

 Nor have we to discuss the partially successful attempts 

 which have been made not to imitate, but to reproduce 

 certain valuable jewels so as to be absolutely identical 

 with the natural stones, not merely in appearance, but 

 in hardness, specific gravity, chemical composition, and 

 behaviour on exposure to air, moisture, or heat. 



One of the earliest successes in this direction was 

 achieved by M. Ebelmen, who produced artificial rubies 

 absolutely identical with natural specimens. His pro- 

 cess, which is too technical to admit of description here, 

 is tedious and necessarily costly. It has not had the 

 slightest influence upon the price of rubies, since the 

 factitious stones, which are mostly small, cost quite as 

 much as natural specimens of the same size. This, by 

 the way, may not impossibly prove to be the case with 

 gold, should its artificial production ever be found prac- 

 ticable — a prospect which the ancient alchemists seem en- 

 tirely to have overlooked. 



Artificial diamonds have also been produced. A few 

 years ago two chemists at Glasgow took up this problem, 

 not, however, working in concert, but employing quite 

 different methods. Both conceived themselves success- 

 ful. But the supposed " diamonds " of one of the expe- 

 rimentalists, on being rigidly tested by experts, proved 

 not to be diamonds at all, but crystals of a very hard 

 form of silica. His rival, however, produced true 

 diamonds, though not of a large size. The process 

 employed is not only difficult, but under possible 

 circumstances even dangerous. Hence the inventor 

 himself declared, in a communication to an alarmed 

 diamond merchant, that he did not for a moment 

 expect that his process could have any practical 

 bearing upon the diamond trade. 



But a very considerable amount of ingenuity is em- 

 ployed, not in either forging or reproducing precious 

 stones, but in improving the colours of such as are 

 obtained in the natural way. Such manipulations are 

 applicable chiefly to stones of the second class, such as 

 chalcedony and its numerous varieties. In its original 

 state, chalcedony is generally white and almost trans- 

 parent. But it is often found yellow, red, or green, and 

 it is then known respectively as jasper or as chryso- 

 phrase. Other varieties are veined, clouded, or banded 

 with several colours, so they are then known as agate, 

 onyx, cornelian, etc. These colours, when not existent, 

 can be produced, and when already present may be 

 heightened and varied by artificial means. These means, 

 it would appear, consist mainly in applying at will pro- 

 cesses which have come into play in the laboratories of 

 nature. 



Stones of this class consist of alternating layers of 

 material, some of which are far more porous and absor- 

 bent than others. Hence such porous layers can be 

 saturated with any desired colouring-matter, whilst the 

 impervious portion remain colourless or retain their 

 original colour. 



A very old method of producing black or dark-brown 



