THE SOLAR MICROSCOPE. 



position in the heavens from minute to minute, the position of the 

 reflector, which at one time would throw the light in the proper 

 direction, would cease to do so after the lapse of a short interval. 

 A proper provision must be made, therefore, by which the position 

 of the reflector may be changed from time to time with the motion 

 of the sun in the firmament, s6 that it shall always reflect the 

 light in a proper direction. 



10. A perspective view of the solar microscope, mounted in the 

 most efficient manner, is given in fig. 2 ; but the principle of its 

 performance will be more easily understood by reference to the 

 sectional diagram in fig. 3, where c c is the condensing lens, H H 

 the mirror which receives the sun's light, and reflects it in the 

 direction of the axis of the tube. This mirror turns on a hinge, 

 by which it may be inclined at any desired angle to the axis of 

 the tube ; and a provision is also made by which it can be turned 

 found the axis, so that its plane may be presented in any desired 

 direction to the sun : a smaller condensing lens is interposed, upon 

 which the rays, converging from c c, are received, and by which, 

 with increased convergence, they are projected upon the opening 

 o o in the slider s s, in which the object is mounted. 

 ' The tube in which the slider s s is inserted, and which carries 

 the smaller condenser, slides within another tube, in the end of 

 which the greater condenser c c is set. By this arrangement, 

 the section of the cone of light, which falls upon the opening o o, 

 may be varied, according to the magnitude of the object. 



The amplifying lens, or lenses, L L, are conveniently mounted 

 in a tube, which can be moved within certain limits to or from the 

 object, so as to accommodate the focus to the position of the 

 screen 1 1, upon which the image is projected. 



After these explanations, the reader will have no difficulty in 

 comprehending the instrument, as shown in perspective in fig. 2. 



Aboard, A A B B, is pierced by a large circular aperture, the 

 diameter of which is a little greater than that of the larger con- 

 densing lens ; a square brass plate, a a b b, to which the micro- 

 scope is attached, is screwed upon this board in such a position, 

 that the condensing lens shall be concentric with the hole in it, 

 and, consequently, that the axis of the instrument shall be at right 

 angles to the board. 



The plane mirror M, by which the light of the sun is reflected 

 along the axis of the instrument, is mounted outside the board 

 A A B B, moving on a hinge, as already described ; and screws are 

 provided at c c', by means of which its inclination to the axis of 

 the microscope can be varied at pleasure, and also by which it can 

 be turned round the axis, the screw which governs its motion 

 moving on the circular opening s D. By these means, whatever 



