MICROSCOPIC DRAWING AND ENGRAVING. 



Fig. 20. 



it near their haunts ; the meal serving the purpose of a bait, they 

 will soon collect upon it; the paper may then be removed, and 

 being placed in a basin, should be 

 brought into the light, when the in- 

 sects will immediately jump from the 

 paper into the basin : they should 

 then be cautiously handled, and 

 placed either in glass tubes or boxes 

 with camphor, to preserve them from 

 other insects. 



These insects, like the Lepisma, 

 are covered with an armour of scales, 

 which, when submitted to the micro- 

 scope, are found to be beautifully 

 striated ; one of them is shown in 

 fig. 20, magnified 550 times in its 

 linear, and, consequently, 302500 

 times in its superficial dimensions. 

 The real length of this scale was 

 the 260th, and its extreme breadth 

 the 700th, part of an inch. 



Smaller, and still more finely 

 marked, scales of the same insect 

 are shown in fig. 21 ; the length 

 of the greater being the 250th, and 



its breadth the 500th, of an inch ; and the length of the lesser the 

 700th, and its breadth the 1375th, of an inch. 



These objects require much greater microscopic power to render 

 visible their minute and beautiful tracery, than such as would suf- 

 fice for the scale of the Lepisma, when submitted to the highest 

 practicable magnifying powers ; they are found to be marked by 

 countless numbers of delicate cuneiform markings, which are seen 

 to stand out in manifest relief from the general ground of the 

 scale. 



