260 ON AERONAUTIC SPIDERS. 
of considerable magnitude, on which the ascending 
current, occasioned by the rarefaction of the air con- 
tiguous 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 to support them and 
they were falling; but scarcely one in twenty con- 
tained a spider, though, on minute inspection, I found 
small winged insects, chiefly Aphides, entangled in 
most of them. 
From contemplating this unusual display of gos- 
samer, my thoughts were naturally directed to the 
animals which produced it ; and the countless myriads 
in which they swarmed almost created as much sur- 
prise as the singular occupation that engrossed them. 
Apparently actuated by the same impulse, all were 
intent upon traversing the regions of air; accordingly, 
after gaining the summits of various objects, as blades 
of grass, stubble, rails, gates, &., by the slow and 
laborious process of climbing, they raised themselves 
still higher by straightening their limbs ; and eleva- 
ting the abdomen, by bringing it from the usual 
horizontal position into one almost perpendicular, 
they emitted from their spinning-apparatus a small 
quantity of the glutinous secretion with which they 
fabricate their silken tissues. ‘This viscid substance, 
