Spiders. 377 



Mr. Blackwall, from subsequent experiments, says he is 

 " confident in affirming, that in motionless air spiders have 

 not the power of darting their threads even through the 

 space of half an inch."* The following details are given in 

 confirmation if this opinion. Mr. Blackwall observed, the 

 1st Oct., 1826, a little before noon, with the sun shining 

 brightly, no wind stirring, and the thermometer in the shade 

 ranging from 55'5 to 64, a profusion of shining lines 

 crossing each other at every angle, forming a confused net- 

 work, covering the fields and hedges, and thickly coating 

 his feet and ankles, as he walked across a pasture. He was 

 more struck with the phenomenon, because on the previous 

 day a strong gale of wind had blown from the south, and as 

 gossamer is only seen in calm weather, it must have been all 

 produced within a very short time. 



" What more particularly arrested my attention," says 

 Mr. Blackwall, " was the ascent of an amazing quantity of 

 webs, of an irregular, complicated structure, resembling 

 ravelled silk of the finest quality and clearest white ; they 

 were of various shapes and dimensions, some of the largest 

 measuring upwards of a yard in length, and several inches 

 in breadth in the widest part ; while others were almost as 

 broad as long, presenting an area of a few square inches 

 only. 



" These webs, it was quickly perceived, were not formed 

 in the air, as is generally believed, but at the earth's surface. 

 The lines of which they were composed, being brought into 

 contact by the mechanical action of gentle airs, adhered 

 together, till, by continual additions, they were accumulated 

 into flakes or masses of considerable magnitude, on which 

 the ascending current, occasioned by the rarefaction of the 

 air contiguous to the heated ground, acted with so much 

 force as to separate them from the objects to which they 

 were attached, raising them in the atmosphere to a perpen- 

 dicular height of at least several hundred feet. I collected a 

 number of these webs about mid-day, as they rose ; and 

 again in the afternoon, when the upward current had ceased, 

 * Mag. Nat. Hist., vol. ii. p. 397. 



