MICROSCOPIC DRAWING AND ENGRAY1NG. 
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 rendei 
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. 
64 
