276 Progress in Science. iApril, 
PHYSICS. 
Licut.—At the late Industrial Exhibition of the Franklin Institute in Phi- 
ladelphia, as also at the like Exhibition of the American Institute in New 
York, silver medals were awarded for the vertical lantern shown in the accom- 
panying figure, which is manufactured by the instrument makers to the 
Stevens Institute of Technology, Hoboken, N.J. The cut shows the appa- 
ratus as adjusted to exhibit on the screen such objects as waves in water, 
cohesion figures, and the like. The light from the lime cylinder or electric 
arc passes through two large lenses, by which it is thrown in a parallel beam 
on an inclined mirror in the triangular box in front. By this it is reflected 
upwards, and is condensed by a large lens standing horizontally on_top of 
© LOANCACRE = CO =e 
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the same triangular box, so as to pass into the objective above, and is then by 
the small upper mirror thrown on a screen. ‘This upper mirror, with the 
objective, is carried by a bar provided «with rackwork, by which an accurate 
adjustment for focus can be made. The objects rest directly on the plate 
holding the large horizontal condenser, When the apparatus is to be used for 
ordinary objects which can be held in a vertical position, a little screw in the 
front of the horizontal plate is taken out, and then the triangular box carrying 
the lower mirror is removed, allowing the horizontal plate to swing down into 
a vertical position, carrying with it the rackwork bar and objective into their 
proper positions. j 
Microscopy.—Mr. T. Charters White, at a recent meeting of the Quekett 
Microscopical Club, gave the results of his experience in maintaining small 
Marine Aquaria, for the purpose of supplying objeéts for a microscopical study. 
Almost any vessel capable of holding a quart or more of water may be made 
use of, although the tank preferred by Mr. White is the well known form 
construéted of slate and glass, divided into two portions by a sloping par- 
tition, on which the rockwork is arranged, the lower part being devoted to the 
storage of sea-water away from the influence of light, and consequently in a 
quiescent state; this arrangement renders the maintenance of the water in a 
healthy condition much easier than when the whole contents of the tank are 
freely exposed. To establish a new aquarium requires considerable care, and, 
ee or 
