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POPULAR SCIENCE REVIEW. 
plished much\more readily . The correction has to be brought into operation,, 
and careful adjustment made, to get the finest result with the English 
lens ; but the German glass has simply to be brought into focus, and the^ 
best result is before the observer, provided that the light has been adjusted, 
in the most efficient manner. It is true that for sharp and perfect definition 
we must be careful to adjust the length of the draw-tube ; in working this 
lens there is much need of attention to this matter ; and speaking from a 
practical point of view, it takes the place, in securing crisp definition, of the 
screw-collar adjustment, although, of course, much easier of application. 
But it is so easy to work the lens with fine results on the more delicate 
tests, that I think that those who make the resolution of these their primary 
object in the possession of a microscope, can scarcely fail in securing their 
utmost desire. It is a glass pre-eminently suited for the resolution of difficult 
lined or beaded objects. 
“ Amphipleura pdlucida is easily resolved into delicate beads when the- 
frustules are moderately coarse ; and almost any that can be met with are 
resolvable into lines ; and this, when these diatoms are mounted in balsam. 
The highest eye-pieces made may be used without any practical detriment 
to the image, although, of course, with a reduced sharpness of definition. 
“ On the whole, I think it in many cases the finest lens, of its power, that 
I have ever seen ; and in every sense it is an admirable acquisition.” 
There is one drawback, viz., that the oil is a solvont of most varnishes and 
gums used in mounting and finishing slides (which may be remedied by 
coating the edge of the cover with shellac varnish) ; and also the neces- 
sity for the objects, such as frustules of diatoms, to be “ burnt ” on to 
the cover or mounted in balsam or other fluid with an equal refractive- 
index. 
MINERALOGY. 
New Minerals from Laangban. — A number of new and interesting 
mineral species from this locality have been described by A. E. Nordenskjold 
{Jahrbuch fur Miner alogie , 1878, 206.) Atopite is the name given to a 
yellowish-brown or resin-brown, semi-translucent mineral which possesses th& 
following composition : 
Antimonic acid . 
72*61 
Lime .... 
17*85 
Iron protoxide . 
2*79 
Manganese protoxide . 
1*53 
Potash 
0*86 
Soda .... 
4*40 
100*04 
The antimony appears to be present in the form of the higher oxide of that 
metal ; and the analytical numbers correspond with the formula 2R0,Sb 2 0 5 . 
Monimolite and romeite are the minerals most closely allied to the new 
species ; it differs from the former in containing no lead oxide and a larger 
proportion of antimonic acid, and from the latter in the ratio of base to acid 
and in the fact that all the antimony is present in the form of antimonic 
