MINERALOGY. 311 



phate, has been found to be very easily made by Friedel and Sarasin. 

 Scorodite, the iron arsenate, has been made by Yerneuil and Bourgeois. 

 Hautefeuille has made leucite, also an iron leucite, that is one which 

 contains iron sesquioxide instead of the usual alumina. Meunier has 

 made enstatite, spinel, and corundum. This does not cover the Avhole 

 list, but it is suflficient to show the energy with which the synthetic 

 method is being pursued in France. 



Some very interesting experiments have been tried in the way of pro- 

 ducing artificially some of the physical features of minerals. Calcite 

 has been noticed to be usually in the condition of polysyuthetic twins 

 when in ordinary limestones, and it has been found that this twinned 

 structure can be induced in a simple crystal by pressing it in certain 

 directions. Baumhauer has shown how to make a perfect artificial twin 

 yet more simply. He takes his jackknife and presses its edge perpen- 

 dicularly into the pole edge of a rhomb near its apex. The parts dis- 

 placed by the jackknife then assume a position with reference to the 

 undisturbed parts as would a rhombohedron twinned with the next 

 more obtuse rhombohedral plane as twinning plane. One can thus easily 

 get a symmetrically formed twin with its re-entrant angle exactly like 

 the calculated angle of the twin. This is a beautiful little experiment 

 that anyone can try in a moment for himself, but to understand its full 

 import and bearing is a deep jjroblem. 



Arclmological Mineralogy. — Under the title of " Nephrite and Jadeite," 

 Prof. Heiurich Fischer has issued a volume which is the second that he 

 has devoted to a description of the results of his studies upon these and 

 other minerals, which in prehistoric times were cut into ornamsnts, 

 amulets, stone axes, &c. He has thus in a systematic manner ii^itro- 

 duced the study of mineralogy into archaeology. With the aid of the 

 microscope and all available scientific resources, he has endeavored H 

 find the nature of the stones most prized b}" the ancients. His long-, 

 continued studies show him that for an insufficiently understood reason, 

 they had a decided preference for green stones, which they brought 

 from most distant lands. The stones mostly obtained and modelled 

 were: green limestones, apatite, green quartz and serpentine, mica- 

 schist, chlorite schists, amazon stone (green feldspar), idocrase epidote, 

 hornblende, and pyroxyne ; and particularly in Asia and New Zealand, 

 the very tough and hard nephrite and jadeite. It will never cease to 

 be a wonder how the ancients so beautifully cut and polished these hard 

 stones with their poor contrivances, and the archaeologists will be thank- 

 ful to this eminent mineralogist who has so carefully determined the 

 mineral nature of so many of their objects of interest, and systematized 

 a great mass of their i)reviousl3^ uninteresting material. 



Other extensive icorJcs. — The fourteenth communication of Mr. W. G. 

 Hankel on the electric properties of minerals has already appeared. 

 He has demonstrated that all minerals possess poles and electric prop- 

 erties of one kind or another, and that the distribution of the electricity 



