206 RIO PLATA. 



the above preparatory steps, connected its legs to- 

 gether with the most delicate threads, but I am 

 not sure whether this observation was correct. 



One day, at St. Fe, I had a better opportunity 

 of observing some similar facts. A spider which 

 was about three tenths of an inch in length, and 

 which in its general appearance resembled a Citi- 

 grade (therefore quite different from the gossamer), 

 while standing on the summit of a post, darted 

 forth four or five threads from its spinners. These, 

 glittering in the sunshine, might be compared to 

 diverging rays of light ; they were not, however, 

 straight, but in undulations like films of silk blown 

 by the wind. They were more than a yard in 

 length, and diverged in an ascending direction 

 from the orifices. The spider then suddenly let 

 go its hold of the post, and was quickly borne out 

 of sight. The day was hot and apparently quite 

 calm ; yet, under such circumstances, the atmo- 

 sphere can never be so tranquil as not to affect a 

 vane so delicate as the thread of a spider's web. 

 If during a warm day we look either at the shadow 

 of any object cast on a bank, or over a level plain 

 at a distant landmark, the effect of an ascending 

 current of heated air is almost always evident: such 

 upward currents, it has been remarked, are also 

 shown by the ascent of soap-bubbles, which will 

 not rise in an in-doors room. Hence I think there 

 is not much difficulty in understanding the ascent 

 of the fine lines projected from a spider's spinners, 

 and afterwards of the spider itself; the divergence 

 of the lines has been attempted to be explained, I 

 believe by Mr. Murray, by their similar electrical 

 condition. The circumstance of spiders of the 

 same species, but of different sexes and ages, being 

 found on several occasions at the distance of many 

 leagues from the land, attached in vast numbers to 



