1114 Journal of Applied Microscopy 



greatest care. This trouble was overcome satisfactorily by dispensing with the 

 flat surfaces ; i. e., by making them on a bevel, with only the sharp edge to 

 reflect the light. 



To do away with the difliculty arising from the small depth of focus, the only 

 way found was to stop down the lens. 



As the depth of some objects is very great in proportion to the focal length 

 of the lens, it necessitates the use of a very small stop. The smallest stop used 

 by me for this work has a diameter of y^f „ of an inch, and the edges of the 

 opening are made nearly sharp and carefully blackened. The rear of the lens 

 has also to be guarded to prevent reflections which in this work would be very 

 serious. Of course, the time of exposure requires to be lengthened in proportion 

 to the size of stop ; many times the exposure has taken over thirty minutes, 

 and as each exposure must be made separately on the plate, the time will be 

 doubled. 



Figure "2. 



Suppose the object to be photographed is a small living insect. It is placed 

 under a tumbler which has a small hole drilled through the bottom. Through 

 this opening is injected a small quantity of ether. This soon places the insect 

 in a condition to be handled. We then set it up on its feet in a position as nearly 

 life-like as possible on a small piece of opalin glass, and, to hold it in position, 

 each of its feet is fastened down by means of wax. This is done by using a very 

 small tool, heated in the flame of a spirit lamp. After the feet are fastened 

 properly, the insect is placed in strong fumes of cyanide of potassium to end its 

 life. The surplus wax is now carefully removed by scraping it away with a fine 

 pointed knife. 



The object is now ready for the camera, and upon the pedestal in front of the 

 lens the mounted object is made fast. The pedestal, upon which the mounted 

 object is fastened, has a rack and pinion movement, so as to elevate the object 

 to the required height, and has also a ball-and-socket joint on the top, so that 

 the object can be placed in any desired position. The image on the focusing 



