CHOICE AND USE OF APPARATUS 



advertise in such papers as Nature^ they all print 

 excellent catalogues, a perusal of which may be 

 a useful preliminary. 



The instrument we select will depend on the use 

 to which we intend to put it and on the length 

 of our purse. Perhaps the question of cost will be 

 more important to most people. An elaborate 

 instrument is not a desirable acquisition, till we 

 are somewhat advanced in our work at anyrate, 

 and one of the models which most makers call 

 Students' Microscopes will do everything we desire. 

 We should have at least two objectives, three if we 

 can afford them, a 1 inch and a J inch will enable 

 us to examine everything described in these pages, 

 except some of the bacteria. If we wish to add 

 a third objective we might select a 2 inch one, for 

 quite low-power work and later we shall probably 

 become the proud possessors of a 1/12 inch objec- 

 tive, but this would be of little use to us at first. 

 Two eyepieces will complete our optical equipment. 

 A condenser for the stage, properly known as a 

 substage condenser is an addition which we shall 

 appreciate, though quite interesting work may be 

 done without it. 



Our other apparatus is inexpensive and comprises, 

 one or two dissecting knives, some needles mounted 

 in handles, a pair of fine scissors, a pair of small 

 forceps, a razor, one or two camel hair brushes, 

 three or four watch glasses, slides and cover slips, 

 and a pipette or two. A pipette, by the way, is 

 merely a glass tube pointed at one end and cut 



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