INTO THE ATMOSPHERE. 
393 
and autumn are those periods. In summer I have fre- 
quently found it utterly impracticable to determine their 
ascent. When they detached themselves, after several vi- 
brations, they have fallen to the ground like a dead weight. 
One day last summer (May) this remarkable fact was de- 
termined in the case of nearly a dozen which I picked up, 
— all that I experimented with on that day. 
The insect would seem to be aware when the threads are 
sufficient for its ascent : perhaps the temporary suspension 
in the horizontal plane may communicate that information. 
The aeronautic spiders make their appearance early in 
the season. One fell on me in the beginning of March last 
(1823), while I was perambulating the streets of Bath. 
I have frequently shewn the phaenomena of the aero- 
nautic spider to my friends, and to Mr T. Hopkins of Kid- 
derminster, and Mr T. Brown of Cirencester. To the lat- 
ter, indeed, I one morning, in a very short period, pointed 
out the phaenomena in five or six different instances. 
Several circumstances concur to shew the phaenome- 
non of ascent to be electric. The propelled threads do not 
interfere with each other ; they are divellent, and this di- 
vergence seemed to proceed from their being imbued with 
similar electricity ; and the character of that electricity ap- 
peared to me to be an interesting subject for subsequent 
research. 
The aeronautic spider, brought near a candle, descends 
by its vertical thread, winds it up, and descends again very 
rapidly and repeatedly. The flame seemed not to attract 
a short upright thread, though the finger brought near, 
did. Placed nearer to the flame, the animal seemed inca- 
pable of descending farther, but moved circularly. 
The point of a gold wire was brought near to the verti- 
cal thread, in one experiment, and above the spider in the 
act of escape to the ceiling of the room. It evidently dis- 
