4.52 Mr. Blackw all's Observations to ascertain 



usual horizontal position into one almost perpendicular, they 

 emitted from their spinning-apparatus a small ({uantity of the 

 glutinous secretion with which they construct their webs. This 

 viscous substance being drawn out by the ascending current of 

 rarefied air into tine lines several feet in length, was carried 

 upward, until the spiders feeling themselves acted upon with 

 sufficient force in that direction, quitted their hold of the objects 

 on which they stood, and commenced their journey by mount- 

 ing aloft. 



Whenever the lines became inadequate to the purpose for 

 which they were intended, by adhering to any fixed body, they 

 were immediately detached from the spinners, and so converted 

 into terrestrial gossamer by means of the last pair of legs, and 

 the proceedings just described were repeated ; which plainly 

 proves that these operations result from a strong desire felt by 

 the insects to effect an ascent. But what, it may be asked, is 

 the exciting cause of this singular propensity? It has been 

 suooested that hummer, or an inclination to procure some fa- 

 vourite kind of food, may supply the requisite stimulus. These 

 suppositions, however, are discountenanced by the plump ap- 

 pearance which the animals exhibit ; by their total disregard 

 of such winged insects as happen to be placed within their 

 power ; by their utter inability to regulate their motions, while 

 atloat, in any other manner than by letting out or drawing in the 

 lines by which they are conveyed through the air, and thus pro- 

 moting their ascent or descent ; by the unsuitableness of the 

 lines for securing their prey ; and lastly, by the uncertainty 

 when a favourable day for their purpose may occur, or even 

 that one may occur at all. 



Were I to hazard a conjecture on the subject, I should be 

 disposed to attribute the manifest anxiety of these insects to 



chanrre 



