334 MOTIONS OF INSECTS. 



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 n*> 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 

 than the air in the air itself*." A writer in the last 

 number of Thomson's Annals of Philosophy b , 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 

 have myself more than once observed these creatures 

 8 Nat. Hist. i. 327. b No. lii. 306. 



