

Sect. XI. 1 



1K)0L0GY 



391 



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of l-lOth, l-i5tli, and l-20th foeal dbtaiices, liaye Icen 

 found most useful by two of the most eminent naturalists 

 in England. With a little practice it is not difficult ^o 

 dissect under the 1-lOth lens, and some succeed under 

 the l"20th. A perse, not having a compound microscope 



All 



might procure a l-30th of an inch Codrington lens 



ast doublet) ghoi 

 same rin^: the 



e 



made to 



on 



sheft. 



opposite end of the horizontal 

 The best sauce. 3 have a flat glass bottom, with 



hould 



c biiU 



thin upright metal sides (silvered wnltbin) ; the 

 be at least tour of themj being in depth (inside measure) 

 S-lOthsj 5-lOths, 7-lOths, and a whole inch. Circular 



of fine-textured cork, of the size of the saucers 



i'T - -_- 



1^' 



cr»ij 



(wit 



of 



o 



bjects 



ad of transmitted light 



and 



lace-needles should 



to be dissected by direct inst 



For this end short fine pins 



b^ procured ; wherever it is possible, the animal ought 



to be fixed to the cork under water. Of the smaller 



plates of gla^:^ of an inch and a half in diameter^ some 

 should be flat and some slightly concave ; the latter are 

 very useful — saucers of this small diameter are incon- 

 venient. 



The simplest and most useful instniments for minute 

 dissection are the triangular glove-needles, which with a 

 little cotton-wool and sealing wax can be easily fixed into 

 pieces of large-bored thermometer tubes ; a stock of 



With 



tubes and needles should be taken on a voyage. 



these needles (by keeping the object only just immersed 



in a drop of water, which can be regidated by the suction 





