202 THE AMERICAN MONTHLY [June 



of the field, focus and adjust the substage, and arrange 

 the illumination easily and eiFectively. 



The camera bellows has an extension of two feet meas- 

 ured from the eyepiece of the microscope to the ground 

 glass. This with a continental-model stand, a two-milli- 

 luetre objective and projection^ or working eyepiece No. 

 4, gives an amplification of one thousand diameters. 

 With lower objectives and less extension of bellows am- 

 plifications ranging down to five diameters may be ob- 

 tained. In focusing the operator can, by standing on 

 a low box, observe the image on the ground glass and 

 manipulate the fine adjustments of the microscope with- 

 out using a focusing rod, though a suitable rod with cord 

 passing around the milled head of the fine-adjustment 

 screw can be easily attached to the upright if desired. 



The Light. — A good and efficient light may be ob- 

 tained by using an oil lamp, or gas or acetylene burner, 

 properly adjusted in the body of a projection stereopticon 

 with the projection ocular removed. 



Of the three acetylene is much the best, and for illumi- 

 nating and actinic power, combined with simplicity of 

 apparatus and management, it is the best artificial light 

 now obtainable for use in photomicrography. It can be 

 easily and safely generated and stored ready for use, its 

 making and use necessitating little if any more trouble 

 than is connected with keeping an oil lamp in order. 

 After experience with sunlight and various artificial 

 lights I until recently settled down to the use of an oil 

 lamp, believing it or gas to give when properly used the 

 best light for practical purposes. Recently I have been 

 using acetylene generated and burned in an apparatus 

 furnished by a concern in Chicago, 111., and find it 

 unequalled for practical work. 



The gas is generated in a small generator and burned 

 in a small burner placed in the lantern body (Fig. 2). If 

 ordinary illuminating gas is used the burner is placed in 



