344 APPENDIX. 



the fine adjustment wheel of the microscope, which is also grooved. 

 The other, a large wooden wheel, is connected permanently by a flat 

 leathern band with a similar wheel attached to the long iron shaft 

 below. 



' The steps in the process of photographing by the above de- 

 scribed apparatus are as follows: The moveable shutter, with the 

 apparatus attached, is buttoned in position, the heliostat set in place 

 on the shelf outside the window and properly adjusted, so as to 

 throw the rays reflected from its mirror upon the microscope mirror 

 at the extremity of the rod on the shutter. The window shutters may 

 now be closed and need not again be opened. The microscope is 

 then placed in the proper position upon the shelf inside the window, 

 and the silk thread adjusted which connects the fine adjustment 

 wheel with the wheel on the edge of the shelf. The operator then, 

 sitting on a stool in front of the microscope, and inserting an eye- 

 piece, views the object as in the ordinary use of the instrument. This 

 he is enabled to do without discomfort or injury to the eye, since the 

 light transmitted by the solution of the ammonio-sulphate of copper, 

 though photographically intense is luminously comparatively feeble, 

 and is also deprived of a large proportion of its heat rays in its pas- 

 sage through that medium. While thus seated at the microscope, the 

 operator makes the necessary adjustments of the stage, achromatic 

 condenser, diaphragms, &c., having perfect control of the illumina- 

 tion by means of the steel rods attached to the mirror without the 

 window and projecting into the room through the shutter. While 

 making these adjustments he commands the fine adjustment wheel by 

 the fingers in the usual way, the wheel readily slipping under the 

 thread that connects it with the wheel on the shelf below. These 

 adjustments being made, the best view and proper illumination of the 

 object secured, the eye-piece is removed, and a black velvet hood 

 attached around the edges of a hinged shelf projecting from the shut- 

 ter (see fig. 417), is lowered so as to envelope all of the microscope 

 but its body, thus preventing any leakage of light by the side of 

 the objective. The operator now goes to the car, adjusts its position, 

 noting its distance from the microscope by the scale on the floor and 

 side of the base of the car, as already described, and clamps it firmly 

 in place. He then sits down behind it and receives the image upon 

 the surface of a piece of plate-glass held in the plate holder, viewing 

 it with an eye-piece held against the glass pla: j, whose focus cor- 

 responds exactly with the anterior surface of this plate. He next 

 turns the milled head that operates on the apparatus for turning the 

 fine adjustment wheel of the microscope, until the image, viewed as 

 just described, appears in exact focus upon the surface of the plate- 



