INFUSORIAL ANIMALCULES. 47 



1-] 000th of an inch. Thus, when the micrometer shall be 

 removed, and an animalcule be put into its place, if the 

 creature subtend five divisions on the card, its size in 

 linear measure will be 5-1000th of an inch. Note The 

 glasses must not be changed during the experiment, nor 

 their distances apart ; neither must the distance between 

 the card and the eye be in any way altered. 



SECTION XVIII. On Glass Tubes, fyc.for taking Infusoria 

 from the Water, and placing them in the Apparatus for 

 examination. 



As these useful little contrivances, which have been be- 

 fore alluded to in this Part, were drawn and described 

 in the Microscopic Cabinet more than ten years ago, it 

 will be necessary merely to mention that little or no im- 

 provement has been made upon them since that period, 

 excepting perhaps that a finer description is found to 

 answer the purpose better than when the larger ones are 

 drawn out at their extremities in the manner there 

 proposed. 



SECTION XIX. On the Compressor, or Crush Box. 



The last remark is equally applicable to the Aquatic- 

 live-boxes, which were described in the Illustrations , 

 1828, and subsequently their different modifications. In 

 order to form an idea of a compressor, or crush-box, you 

 must suppose that the cover of the live-box is so adapted 



