Itctrospcctlve Critichm. 397 



the atmosphere, Mr. Murray seems to think " sadly complicated and con- 

 fused;" yet in his former letter (Vol.1, p. 321.) he allows that spiders, 

 when afloat, obey the direction of the breeze, and that they frequently move 

 in lines inclined at various angles to the plane of the horizon. Now, sup- 

 posing that they are raised into the atmosphere by the agency of electricity, 

 as Mr. Murray conjectures, and are also liable to have their motions in- 

 fluenced by currents of air, which he does not attempt to deny, complicated 

 and confused as the doctrine may appear to him, I do maintain, that, on his 

 own showing, spiders, so circumstanced, are subject to the laws of compound 

 forces. How, indeed, can he account for the oblique directions in which he 

 has seen them sail through the atmosphere, except on the principle which I 

 have pointed out ? Let him reject that, and his electrical hypothesis will 

 avail him little. 



Mr. Murray's felicitous manner of stating his experiments is again illus- 

 trated in the following example : — " Last autumn," he writes, " I let go an 

 aeronautic spider, together with some thistle downy simultaneously from the 

 same spot in the open air. They moved in exactly contrary directions ! I must 

 leave the phenomenon with Mr. Blackwall, to be adjusted by the laws of 

 compound forces." It may be very convenient for Mr. Murray to leave to 

 the explanation of others, those phenomena of which his own hypothesis 

 affords no satisfactory solution ; but then the least he can do is to supply the 

 requisite data. Did the objects submitted to this experiment move in the 

 same vertical line, or in horizontal or oblique directions ? On these points 

 Mr. Murray gives no information, and yet it is essential that they should be 

 understood, before an explanation can even be attempted, as several widely 

 different cases immediately present themselves to the mind of the investi- 

 gator. I beg to inform Mr. Murray, however, that I am not in the habit of 

 essaying the exposition of imperfectly described phenomena, the accuracy of 

 which I have no means of verifying. Nothing caa be more amusing than the 

 satisfaction with which Mr. Murray affects to sneer at ray application of the 

 laws of compound forces, since it will be perceived, from the preceding 

 paragraph, that, in so doing, he is directing his sarcasms against the employ- 

 ment of a principle, the influence of which he himself has unwittingly ad- 

 mitted. 



It is somewhat remarkable, that Mr. Murray should let my " asserted 

 fiacts," as he thinks proper to term them, remain so long without investi- 

 gation ; especially as they must, if established, totally subvert his electrical 

 hypothesis. Such an omission is the more extraordinary, as there can be no 

 obstacle to the repetition of my experiments, which are circumstantially de- 

 tailed, and may be conducted without difficulty. I still continue to multiply 

 them on all occasions, and uniformly with the same success. I am con- 

 fident therefore in affirming, that, in motionless air, spiders have not the 

 power of darting their threads even through the space of half an inch. Let 

 not Mr. Murray complain that my last letter leaves this question exactly as 

 it was ; while the above decisive fact remains unshaken, it would be per- 

 fectly useless to embarrass him with any new matter. 



However reluctant Mr. Murray may be to satisfy himself of the accuracy 

 of the facts which I have advanced, I can assure him^ that no such feeling 

 has existed, on my part, with regard to the examination of his experiments, 

 whenever this has been practicable. I have carefully repeated several of 

 them, and am compelled to say that the results at which I have arrived 

 differ widely from those obtained by him. In his Experimental Researches, 

 p. 125., Mr. Murray asserts that the ascent and movement of the aeronautic 

 spider in the atmosphere are essential to its very existence ; and again, p. 128., 

 he observes that he has invariably found that it is impatient of confinement, 

 « and will die, whether imprisoned in a chip box or glass tube (showing that 

 light does not affect the question), sometimes in twenty hours, or at most in 

 iivo or three days'' In order to try the soundness of these opinions by the 



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