THE SOLAR MICROSCOPE. 
An opening being provided in a convenient position in one of 
tbe window-shutters, corresponding in magnitude with the aper¬ 
ture in the hoard aabb, the latter is screwed upon the window- 
shutter, so that the two openings shall coincide. The mirror M 
will then be outside the window-shutter, while the instrument 
and its appendages will be inside. The window selected should, 
ofcourse, be one having such an exposure that the sun’s rays 
can be reflected by the mirror in the direction of the axis of 
the tube. 
12 . To adjust the instrument, remove the piece L T , which sup¬ 
ports the slider, so that the light may pass unobstructed to the 
amplifying lens. By varying the position of the reflector M, by 
means of the milled heads c c', a position will be found in which 
a uniformly illuminated disc will appear on the screen; this disc 
may be rendered more clear and distinct by adjusting the in¬ 
strument by means of the rack and pinion attached to the tube. 
When these preliminary adjustments are made, the piece N is 
replaced, and an object inserted in it; the instrument being then 
more exactly focussed, a distinct image of the object, upon a large 
scale, will be seen on the screen. 
The management of the instrument will vary with the nature of 
the object. If it be a very transparent one, a strong light thrown 
upon it would cause it almost to disappear. The light, therefore, 
in such case, must be so regulated as to produce the image in the 
most favourable manner, which may always easily be accomplished 
by moving the tube t' in and out of the tube t, until the desired 
result is obtained. 
When the experiments are continued for any considerable 
interval, it will be necessary, from time to time, to accommodate 
the reflector M to the shifting position of the sun, which may 
always be done by the milled-heads c c'» This adjustment, how¬ 
ever, might be superseded by mounting the mirror m upon an 
apparatus called a Heliostat, the effect of which is, to make the 
mirror move with the sun, by means of clock-work. Such an appa¬ 
ratus, however, is expensive, and the adjustment above described 
is attended with no great inconvenience or difficulty. 
13 . The substitution of the oxy-hydrogen, or electric light, for 
the sun in this most instructive instrument, renders those who 
use it, however, altogether independent of the sun, so that it can 
be used for a night as well as a day exhibition. Since the method 
of applying to it the electric light has been already described very 
fully in our Tract upon the Magic Lantern, the explanation need 
not be reproduced here. 
184 
