274. Scientific Intelligence. 
It is massive, with an indistinct fibrous structure : color, iron- 
gray: streak, dark clove-brown: luster, metallic: acquires a beau- 
tifully irised tarnish—the colors being various shades of yellow, 
green, blue, and purple. Mr. R. A. A. Johnston found it to have 
a specific gravity (after correction for a little intermixed quartz), 
at 15°5° C., of 5°082. An analysis by him, upon carefully selected 
material, g cave the results of 1; and deducting the gangue (silica) 
and recalculating the remaining constituents for one hundred 
parts those given in II are obtained. 
S Sb AS Cu Ag’ Pb. ‘Zn Ne i@irartz 
T2059 26°81] 0°22 21°03 10°64 8:91" 5S! 0:88" Saat oteiG 
TL. 21°68), 28°22: 0:23 22°14 111°20) 9°38) (6224 0-33E= ag 
7. Minerals and how to study them: A book for beginners in 
Mineralogy ; by Enywarp Sarispury Dana. 380 pp. New York, 
1895 (John Wiley & Sons).—This is a small work on Miner alogy 
of very elementary character, the scope of which may be made 
sufficiently clear by the following quotation from the Preface :— 
“ The author has occupied some hours, which could not be devoted 
to more serious labor, in preparing this little book, in the hope 
that it might serve to encourage those who have a desire to learn 
about minerals, and also to increase the number of those whose 
tastes may lead them in this direction. He shares with most 
teachers at the present time, the conviction that the cultivation 
of the powers of observation is a most essential element in the 
education of young people of both sexes; he believes further, 
that no subject is better fitted to accomplish this object and at 
the same time to excite active interest than that of Mineralogy. 
The attempt has been made to present the whole subject in a 
clear, simple and so far as possible, a readable form, without 
cheapening the science. As the understanding of the different 
parts of the subject requires some preliminary knowledge of 
physics and of chemistry, a little elementary matter in these 
departments has been introduced.” 
8. The Constitution of the Silicates ; by F. W. Crarxe.: 
Bulletin of the U. 8. Geological Survey, No. 125, 109 pp., Wash- 
ington, 1895.—This bulletin, recently issued, contains a detailed 
statement of the author’s views upon the chemical constitution 
and structural formule of the silicates. Numerous articles by 
the author upon parts of this subject have from time to time 
appeared, many of them in this Journal; but all interested will 
be glad to find here a full presentation “of the conclusions to 
which his study as well as his admirable experimental work have 
led. While he does not claim that the last word has been said 
upon this subject, this contribution to the most important and 
difficult part of mineral chemistry is of very high value and 
throughout both suggestive and helpful. 
9. Native Silica: a treatise upon a series of specimens of 
Quartz, Rock crystal, Chalcedony, Agates and Jaspers, etc.; 
with a descriptive catalogue of the specimens forming the collec- 
tion of the late Right Hon. the Earl of Derby, K. G., by Brycz 
Wricut, F.R.G.S. 263 pp. 8vo. London, 1894 (Wyman & Sons). 
—This is a handsomely printed catalogue containing, besides the 
