346 IXSECT ARCHITECTURE. 



approach of rain, and the index of De Saussere's 

 hygrometer rapidly advancing towards humidity, the 

 spider is unable to ascend."* 



Mr Murray had previously told us, that " when 

 a stick of excited sealing-wax is brought near the 

 thread of suspension, it is evidently repelled; con- 

 sequently, the electricity of the thread is of a nega- 

 tive character," while " an excited glass tube brought 

 near, seemed to attract the thread, and with it, 

 the aeronautic spider, "t His friend, Mr Bowman, 

 further describes the aerial spider as " shooting out 

 four or five, often six or eight, extremely fine webs 

 several yards long, which waved in the breeze, 

 diverging from each other like a pencil of rays." 

 One of them " had two distinct and widely diverging 

 fasciculi of webs," and " a line uniting them would 

 have been at right angles to the direction of the 

 breeze. "J 



Such is the chief evidence in support of the elec- 

 trical theory; but though we have tried these ex- 

 periments, we have not succeeded in verifying any 

 oijie of them. The following statements of Mr 

 Blackwall come nearer our own observations. 



5. " Having procured a small branched twig," says 

 Mr Blackwall, " I fixed it upright in an earthen 

 vessel containing water, its base being immersed in 

 the liquid, and upon it I placed several of (he spiders 

 which produce gossamer. Whenever the insects 

 thus circumstanced were exposed to a current of air, 

 either naturally or artificially produced, they directly 

 turned the thorax towards the quarter whence it 

 came, even when it was so slight as scarcely to be 

 perceptible, and elevating the abdomen, they emitted 

 from their spinners a small portion of glutinous 



* Loudon's Mag. of Nat. Hist., vol. i. p. 322. 

 t Expeiim. Researches in Nat. Hist., p. 136. 

 % Mag. Nat. Hist., vol. i. p. 324. 



