SPIDERS. 345 



spins a long thread, there is a certainty of fine weather 

 for at least ten or twelve days afterwards."* A 

 periodical writer, who signs himself Carolan,*!* 

 fancies that in darting out her thread the spider 

 emits a stream of air, or some subtile electric fluid, 

 by which she guides it as if by magic. 



A living writer (Mr John Murray), whose learn- 

 ing and skill in conducting experiments give no 

 little weight to his opinions, has carried these views 

 considerably farther, " The aeronautic spider," he 

 says, " can propel its threads both horizontally 

 and vertically, and at all relative angles, in mo- 

 tionless air, and in an atmosphere agitated by 

 winds; nay more, the aerial traveller can even dart 

 its thread, to use a nautical phrase, in the ' wind's 

 eye.' My opinion and observations are based on 

 many hundred experiments The entire phe- 

 nomena are electrical. When a thread is propelled 

 in the vertical plane, it remains perpendicular to the 

 horizontal plane, always upright, and when others 

 are projected at angles more or less inclined, their 

 direction is invariably preserved; the threads never 

 intermingle, and when a pencil of threads is propelled, 

 it ever presents the appearance of a divergent brush. 

 These are electrical phenomena, and cannot be ex- 

 plained but on electrical principles." 



" In clear, fine weather, the air is invariably 

 positive; and it is precisely in such weather that the 

 aeronautic spider makes its ascent most easily and 

 rapidly, whether it be in summer or in winter." 

 " When the air is weakly positive, the ascent of the 

 spider will be difficult, and its altitude extremely 

 limited, and the threads propelled will be but little 

 elevated above the horizontal plane. When negative 

 electricity prevails, as in cloudy weather, or on the 



* Brez. Flore des Insectophiles. Notes, Supp. p. 134. 

 t Thomson's Ann. of Philosophy, vol. iii, p. 306. 



