USE OF THE CAMERA. 10 1 



costing only twenty-one marks (^5.25). Most students at first 

 find it difficult to use a camera, but practice soon overcomes 

 the difficulty and enables one to adjust the illumination prop- 

 erly, which otherwise is the principal cause of poor success. 



The other accessories for the microscope which are of 

 value to the biologist are a stage micrometer, one or more 

 animalcule cages, glass cells, a compressorium (the one des- 

 cribed by Mr. Ryder* possesses many advantages and is on 

 the whole the best) , and a bull's eye condenser which is neces- 

 sary with opaque objects, and when using the higher powers. 

 The polariscope is of use in mineralogy and in differentiating 

 some animal tissues. Rotary stages, unless accurately cen- 

 tred, are useless and then are of value only to the mineral- 

 ogists. The stage forceps which accompany most stands are 

 models of clumsiness, are wholly worthless, and can well be 

 dispensed with. 



In writing the foregoing pages on the microscope and its 

 accessories, the writer has had this object in view : to show 

 that the simpler an instrument is, other things being equal, 

 the better it is, and that none need be deterred from purchas- 

 ing a microscope on the grounds that a good instrument 

 costs an outrageous amount. Just as soon as American stu- 

 dents realize that the simpler their apparatus is the better 

 their work will be, just so soon will American science rise 

 from its present low level. 



There are three men in America, who never did a single 

 stroke of original work in their lives, to whom we are in- 



* American Naturalist, xiv, p. 691. z88o. 



