fSGO Retros2iective Criticism, 



■he should wish to shield his paper behind a screen, when he alone is re- 

 sponsible for the acts of his own offspring. 



Mr. Blackwall assures us, he was unacquainted with Gay Lussac's ac- 

 count of the ascent of the soap bubble, and we have a right to believe his 

 statement ; the principle, though he confesses it, has not novelty to recom- 

 - mend it ; he applies it to the ascent of the spider, exactly as that eminent 

 philosopher applied it to the soap bubble, and I must really leave Mr. 

 Blackwall to manage the tackling of his composition of forces, as best he 

 may. To me at leasts it seems sadly complicated and confused. 



Mr. Blackwall seems really to consider my observations as almost per- 

 sonal against himself; but I can assure him that this is not even possible, 

 since I never even met with his name previously to seeing it in the TranS' 

 actions of the Linnean Society ^ in a paper on the ascent of the spider which 

 purports to bear his name. 



Because I did not mention the temperature within and without, ergo I 

 had not taken it, and had not ascertained the direction of the current. 

 Now, Mr. Blackwall may have, if he presses for it, all the benefit that may 

 arise from his illogical conclusion. 



It seems that Mr. Blackwall did not mean to canvass the electrical aip- 

 titude o^ the mr as to its positive or negative relations; but only that the 

 aeronautic spider is not particularly select in the quantity or intensity that 

 may abound. 



As Mr. Blackwall is very sensitive about his name being introduced into a 

 question which has, or ought to have, truth for its aim and object, he should 

 have been a little more cautious in rejecting the opinions of those who 

 have investigated the subject with as much care as himself; and I must 

 confess that, in that very memoir, I can perceive but little courtesy ex- 

 hibited toward his fellow-labourers in the delightful field of natural history, 

 and in the case of those who have canvassed the subject. 



I have " committed" my opinions to the same test which must be ap- 

 plied in the case of his asserted facts; by that standard of appeal we 

 must both submit to be judged, and receive our acquittal or condemnation 

 accordingly, and it is needless for either him or me to endeavour to fly off at 

 a_tangent. I merely repeat that my experiments have been numerous and 

 diversified, and all those who know me will concede to me the merit of an 

 indefatigable, laborious, and careful experimenter ; and when that volume 

 is reprinted I shall be able to adduce a multitude of facts more. 



Last autumn I let go an aeronautic spider, together with some thistle^ 

 down, 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." I, however, 

 did not ascertain the temperature. I remain, Sir, yours, &c. — J. Murray, 



The Lump attached to the Throat of the Hare. (Vol. I. p. 216.) — Sir, In 

 confirmation of the opinion which I was led to form in my communication 

 to you respecting the hare, that the lump attached to its throat was most pro- 

 bably caused by a diseased state of some of the glands, and was not an original 

 deformity from its birth, I had the good fortune to meet with the following 

 parallel case in one of the feathered tribe, a common hen (Phasianus Gallus), 

 and as it appears to be a novel circumstance, and may assist the mind in 

 forming a just conclusion as to the cause of that singular appearance, I hope 

 I may secure for the following description of it, a place in the next Num- 

 ber of your Magazine : — Happening to find the hen just as she was dying, 

 and perceiving that she was expiring from suffocation,! felt curious to ascer- 

 tain the immediate cause by which her breathing was affected ; and my 

 curiosity was not a little increased by the person who had the charge of her 

 informing me, in answer to my queries, that she had a large lump in her craw. 

 This lump I at first supposed to have been occasioned by swallowing some- 



