44 



current, " either naturally or artificially produced." It 

 is also assumed, that " this velocity is equal, or nearly 

 so, to that with which the air moves ;" though such 

 a ratio of correspondence, traced to its exciting cause, 

 is not so clear. However, this observer persists in 

 " affirming that, in motionless air, spiders have not the 

 power of darting their threads through the space of half 

 an inch ; " or, in other words, we infer, of not being able 

 to " dart" their threads at all ; and Mr. Rennie, in kind 

 and faithful echo, adds, " we are quite certain that it 

 cannot throw out a single inch of thread without the 

 aid of a current of air." The latter is of opinion, 

 that " the globules, being carried up by the current 

 of air," are thus " drawn out into a thread : " but how 

 this can be effected counter to such a current, is not 

 so easily imagined. However, Mr. Rennie, on " pro- 

 ducing a stream of air, by blowing gently towards its 

 position," " had the pleasure of seeing a thread 

 streaming out from them" (the " spinnerets ") ; and 

 he was " convinced " also, " that it was the double or 

 bend of the thread which was blown into the air :" 

 and then follows a " reason" for the spider's doing so. 

 The premises on which these conclusions are founded 

 do not appear to us by any means quite so satisfactory 

 as they do to these observers. Some spiders being 

 imprisoned under a bell-glass, projected no threads 

 whatever ; and it is thus concluded they were unable 

 to do so. This opinion, however, is scarce warrantable. 

 It is not doubted that these insects are sagacious 

 creatures, and might in this case, also, have a " reason" 

 for not making the useless attempt : they surely saw 

 that a crystal hemisphere bounded their pathway, and 

 that their imprisoned space was circumscribed ; and all 

 this cunning might be reasonably assigned to them, 

 without extending their sagacity to the amount of 



