70 ELEMENTARY PHOTO-MICROGRAPHY. 



flea, podura scales, and sections of wood are well- 

 known objects for such a purpose. 



Abbe's test plate is perhaps the best for high 

 powers, though reliable and comparative results 

 can only be obtained after considerable experience 

 with this piece of apparatus. 



DIATOMS AS A HOBBY. 



Every possessor of a microscope is sure at some 

 time or other to dabble in diatoms a group of 

 unicellular plants to be found wherever there is 

 salt or fresh water or damp earth and for photo- 

 graphic purposes no better objects could be desired. 

 In size they are so tiny as to be almost invisible 

 to the naked eye, yet marked with exquisite 

 patterns of delicate and intricate lacework that 

 attract both novice and specialist alike, and make 

 them the playthings of a microscopist. 



Evidently, therefore, Nature does not lavish 

 its gifts of beauty through processes of evolution, 

 for nothing prettier can be found in highly 

 organised structures than in these simple cells 

 of the vegetable kingdom. 



When viewed in a living state, a drop of water 

 may show diatoms moving about in numbers and 

 kept free from collision by some mysterious 

 agency not yet known. It is not the living plant, 

 however, so much as its siliceous skeleton in a 

 prepared state that makes it dear to the micro- 



