338 MOTIONS OF INSECTS. 
you will take them into your hand. Last summer one 
alighted on my book as I was reading in the parlour ; 
and running to the top of the page and shooting out a 
web, took its departure from thence. But what I most 
wondered at was, that it went off with considerable velo- 
city in a place where no air was stirring; and I am sure 
that I did not assist it with my breath. So that these 
little crawlers seem to have while mounting some loco- 
motive power without the use of wings, and move faster 
A writer in the last 
9 
than the air in the air itself*. 
number of Thomson’s Annals of Philosophy, under the 
signature of Carolan, has given some curious observa- 
tions on the mode in which some geometric spiders shoot 
and direct their threads, and fly upon them; by which 
it appears, that as they dart them out they guide them 
as if by magic, emitting at the same time a stream of air, 
as he supposes, or possibly some subtile electric fluid. 
One which was running upon his hand, dropped by its 
thread about six inches from the point of his finger, 
when it immediately emitted a pretty long line at a right 
angle with that by which it was suspended. This thread, 
though at first horizontal, quickly rose upwards, carry- 
ing the spider along with it. When it had ascended as 
far above his finger as it had dropped before below it, it 
let out the thread by which it had been attached to it, 
and continued flying smoothly upwards till it nearly 
reached the roof of the room, when it veered on one side 
and alighted on the wall. In flying, its motion was 
smoother and quicker than when a spider runs along 
its thread. He observes, that as the line lengthens be- 
hind them, the tendency of spiders to rise increases.—I 
4 Nat. Hist. 1. 327. » No. li. 306—. 
