On the Aerial Spider, 321 



Mr. Blackwall concludes that the flight of the spider originates 

 in a similar cause. 



Contrary to the assertion, that " spiders have no power of 

 propelling their webs without assistance from the wind," I 

 fearlessly maintain that they can do so in an atmosphere in 

 which the very leaf of the aspen remains motionless; and 

 although their cJiar volant obeys the direction of the breeze, this 

 simple fact proves nothing in favour of the opinion advanced 

 by Mr. Blackwall. The aeronautic spider can propel its 

 threads both horizontally and vertically, and at all relative 

 angles, in motionless 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 hundreds of experiments ; 

 on favourable occasions I am constantly extending their 

 amount; and as often do I find my deductions supported, 

 namely, that the entire phenomena are electrical. My infer- 

 ences, therefore, have not been hastily drawn. 



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 pheno- 

 mena, and cannot be explained except on electrical principles. 



The specific gravity of the insect, with its web, are very 

 superior to that of the atmosphere, and without some exotic 

 power imparted to them, their rise in the atmosphere would be 

 impracticable ; and though a film inflated with heated, and of 

 course, rarefied air, would certainly ascend, it is more difficult 

 to undersand how a solitary thread, so fine, could be thus 

 acted upon by any current of air, whether heated or not, so as 

 to determine its buoyancy and ascent. And so far from the 

 unattached cobwebs, which are occasionally seen to float in 

 the atmosphere, having been " raised from the surface of the 

 ground, by the action of air highly rarefied by a cloudless sun," 

 such threads will be seen to fall in the warmest weather, and in 

 all the unclouded radiance of the sunbeam. But this phenome- 

 non presages rain, and is its precursor. The electrical character 

 of the atmosphere has changed from positive to negative. 



These interesting aeronauts sometimes rise with the rapidity 

 of an arrow in the zenith of the observer ; at other times, they 

 are seen to float parallel with the plane of the horizon ; and 

 again, at variously inclined angles. Sometimes the ascent is 

 extremely slow. An ascending current of warm air, it is con- 

 ceivable, might effect a vertical movement; but how it could push 



Vol. L — No. 4. z 



