52 



the top of houses, churches, and steeples. That they 

 have not legs for travelling so far, is manifest : it is 

 therefore probable, either that they dart out webs, 

 and can make themselves buoyant, and lighter than 

 the air : or that their bodies are naturally lighter than' 

 air, and so they can swim from place to place. 

 It is highly probable, the eggs of such as are ovipa- 

 rous may be light enough to float therein. 



To trace this matter farther : every one must have 

 observed threads floating in the air : but few consider 

 what end they serve. They are the works of spiders. 

 Their usual method is, to letdown a thread, and then 

 draw it after them. But in the midst of this work they 

 sometimes desist ; and turning their tail accord- 

 Ing to the wind, emit a thread with as great violence, 

 as a jet of water discharged from a cock. Thus they 

 continue darting it out, which the wind carries for- 

 ward, till it is many yards long. Soon after, the spi- 

 der throws herself oft from her web, and trusting her- 

 self to the air, with this long tail, will ascend swift, 

 and to a great height with 'it. These lines, which 

 the spiders attach to them (though unobserved) make 

 these air-threads, that waft them along the air, and 

 enable them to prey on many insects, which they 

 could not reach by any other means. 



All spiders that spin, young as well as old, cast out 

 their threads, and sail thereby in the air. And the 

 threads themselves shew the use thereof, being usually 

 with the fragments of devoured animals. 



When the thrtftls are newly spun, they are always 

 single, and are generally seen ascending higher and 

 higher. But when they are seen coming down, they 

 are sometimes composed of three or four, and either 

 without any spider or with several. It is plain this 

 happens from the threads meeting and entangling in 

 the air, which of course brings them down. 



It is common to see a spider mount to the topmost 

 branch of a bush, and from thence dart out several 

 threads one ofter another, trying as it were, how she 

 likes t^era. When she had darted one several yards. 



