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POPULAR SCIENCE REVIEW. 
of two varieties of this sand is quoted percentically, care being taken to 
analyse separately the magnetic and non-magnetic portions. The following 
quotation will give an idea of the composition of this material as met with 
at Punta Arenas (on the Straits of Magellan) : — Non-magnetic portion — 
Titanic acid, 19’2 ; protoxide of iron, 29*7 ; peroxide of iron, 49-7 ; lime, 
09 ; magnesia, 1*0. Magnetic portion — Titanic acid, 22*8 ; protoxide, 
1 5*8; peroxide of iron, 61*5. 
A Collection of Russian Minerals. — According to the Scientific American , 
the Russian Government has recently presented to the cabinet of the School 
of Mines, of Columbia College, U.S., a very choice collection of minerals. 
Conspicuous among them are nuggets of native gold, native platinum, iridos- 
mine, large emeralds from the Urals (single and in clusters in the gangue), 
topaz, chrome garnet, malachites, &c. ; in all 456 rare specimens. 
Extracting and Separating Copper. — Mr. J. Elkington is the author of a 
paper in the Revue hebdomadaire , May 19, on the processes employed for 
this purpose. The principle applied by the author consists in employing 
electricity for dissolving the copper contained in the crude metal obtained 
by the usual smelting methods, and for depositing that metal galvanically 
upon plates of copper, causing the other foreign metals to fall to the bottom 
of the vessels in which the operations take place. Copper, containing very 
small quantities of silver, may be advantageously treated thus for the 
recovery of the last-named metal. 
Two Cornish Minerals. — At the meeting of the Chemical Society on 
May 5 Professor Church communicated the analysis of two Cornish minerals. 
The one, restormelite, was obtained from the Restormel Iron Mines, and 
may be regarded as a variety of kaolinite, standing nearest to the lithomarge 
group. Its specific gravity and its hardness are nearly the same as those of 
lithomarge. In its percentage of silica and alumina (its chief constituents) 
it does not differ from that of lithomarge ; but, while restormelite contains 
7 per cent, of soda and potash, lithomarge contains a mere trace of these 
alkalies. Mr. Church considers restormelite as preserving in its alkalies 
more evident traces of its felspathic origin than we usually find in such 
alteration-products. The percentages obtained in six analyses were then 
stated. 
MICROSCOPY. 
Mr. Holmes's New Binocular. — Mr. Samuel Holmes has constructed a 
binocular by contriving to divide the object-glass along its whole length, 
and so splitting the pencil of light into two, which pass along two tubes to 
the two eyes. The following is the description of the instrument : — u My 
invention consists in the use of two object-glasses, or portions of two object- 
glasses, or of one object-glass divided into two parts, to supply through two 
eye-pieces a binocular and stereoscopic view of opaque or transparent micro- 
scopic objects while illuminated by reflected or transmitted light, and also 
in the use of certain mechanical means herein described, or their equivalents, 
for securing the motion in required directions, or rest in necessary positions 
of the optical parts of such combinations for obtaining monocular or 
