"This experiment, which, from want of due precaution, has misled so many distinguished naturalists, I have tried with several geometric spiders, and always with the same success."[FE] 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."[FF] The following details are given in confirmation of 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 perpendicular 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, and they were falling; but scarcely one in twenty contained a spider: though, on minute inspection, I found small winged insects, chiefly aphides, entangled in most of them.