43 



that of the ascent of a balloon ; and Mr. Blackwall's 

 hypothesis of heated currents becomes at once super- 

 fluous and unnecessary: but it does occur, that the 

 thread is not specifically lighter than the air, but so 

 much heavier, that it immediately falls to the ground, 

 unless electrified, when it floats, or is borne up by 

 some other buoyant principle. " It is now generally 

 admitted," says this able author, " that several kinds 

 of spiders have a power of darting out a thread in 

 any direction, and to a comparatively great distance. 

 The mechanism, however, of this extraordinary effort 

 is not at all understood." This is an opinion charac- 

 terised by a laudable philosophical caution ; and he 

 also expresses a doubt, notwithstanding what Mr. 

 Blackwall has advanced on the subject, in his paper 

 published in the Linnaean Transactions, whether the 

 gossamer of the morning is ever carried up into the 

 air. Indeed a suspicion and scepticism may be very 

 naturally indulged on this question, since the gossa- 

 mer-web seems to remain just as it was, though not so 

 visible to the eye, after the entangled dew has exhaled 

 from it in the sunbeam ; and, indeed, so firmly cemented 

 to the spikes of grass are those threads, that they 

 cannot be detached entire. 



There are two distinct phenomena connected with 

 this little aeronaut, which may be considered independ- 

 ently of each other. The first is, the power of pro- 

 pelling the threads into the air, and the principle by 

 which it is excited ; and the second, the cause which 

 promotes its ascent. Mr. Blackwall considers, in re- 

 ference to the first, that " air sensibly agitated " is 

 necessary to the projectile power, when the thread is 

 then " carried out in a line." We confess, however, 

 that to us it is not quite so obvious, how this effect 

 should be produced in the " wind's eye " of any such 



