Retrospective Criticism, 189 



Coquimbo owl, being two very different animals, are, in the heading, stated 

 to be one and the same thing. The passage quoted relates to the Biscacho, 

 an animal described by Captain Heatl as resembling a rabbit, but which, in 

 the passage I allude to, is called " a bird." The description runs through- 

 out of the Biscacho, but the drawing is that of the owl. — M. January y 

 1830. 



The Aerial Spider. — Sir, My devotedness to experimental electricity, for 

 the last fifteen years, should certainly, at any rate, have gained for me the 

 requisite qualification for investigations like these, and I therefore cannot 

 cede to an assertion evidence gained through the medium of experiments 

 diligently and carefully conducted. Atmospherical electricity has been with 

 me a favourite study, and I trust it is one in which I find myself in some 

 degree at home ; and the employment of Coulemb's Balance of Tarsim, 

 with Breguet's Thermometre metalliqiie, has been of essential service to me. 

 Professor Brande has justly concluded that the divergence of the threads 

 in the fasciculi represented by Mr. Bowman's diagram can scarcely be 

 otherwise explained ; and a very slight excess of electricity in the excited 

 substance employed as a test for the electric condition of the thread, every 

 electrician knows, would defeat the end proposed. Is Mr. Blackwall aware 

 of this, and have his experiments been thus secured ? A spider's thread, 

 darted through the air, must necessarily acquire electricity from the friction 

 occasioned by its impulse through that medium j and, if propelled counter to 

 a current, the amount of excitement will be greater ; a thread of glass is 

 excited under such circumstances. Is Mr. Blackwall ignorant that a cuiTent 

 of air is an excitant of electricity ? a fact long ago proved by Bennet and 

 other electricians. The air issuing from the nozzle of a pair of common bel- 

 lows, and directed on the cap of the electroscope, will occasion a divergence of 

 its pendent leaves. Now, Mr. Blackwall should have known all this : and, 

 permit me to ask, what connection is there between heated currents emanating 

 from the earth and an impulse of air, even on INIr. Blackwall's own showing V 

 I am not disposed to yield to Mr. Blackwall in electrical experiment ; and 

 those who have witnessed my illustrations of this branch of science will rea- 

 dily, if I mistake not, give me credit for successful and delicate manipulation. 

 I am in possession of attestations, from other sources than my own, in veri- 

 fication of the asserted fact of the short-lived term of existence, in the case 

 of the darh-broimi glossy gossamer sjnder, when imprisoned within narrow 

 precincts, as a small chip box, or tube of glass ; and I would just say to 

 others (certainly not Mr. Blackwall) exjyerimentum fiat, I have found the 

 result, in nearly twenty cases, with this variety, and have not made the 

 experiment with any other. The " shy retu'ing truth," however, gleams in 

 his own account of the matter ; though 



" He that's convinced against his will. 

 Is of the same opinion still." 



If my antagonist can satisfactorily confute the facts and phenomena 

 recorded in the volume referred to, he is a more profound wit than I 

 have hitherto given him credit for. This notice, however, is final on my 

 part. Mr. Blackwall may continue his appeals to the Council of the Lin- 

 nean Society, or to the individual authority of Humboldt : I protest, how- 

 ever, against being esteemed accessary to any opinion that would suppose me 

 to think by proxy. I am. Sir, &c, — J. Murray. Nov. 19. 1829. 



Mr. Palmer of ChigweWs Lists of Plants. — Sir, In reading your last Number of the Magazine of 

 Natural Hi.<tory, I must beg leave to say, I was rather surprised to see, among the plants collected 

 by the Rev. S. Palmer of Chigwell, Essex, many that are, I believe, every where almost, in this 

 country, of very common occurrence. Localities of such plants, I humbly conceive, cannot be of 

 any service. Thymus N&peta. is mentioned, and marked with a star, as being rather uncommon, 

 while Ver('mica spicata, certainly a much more local plant, is not so distinguished. If ever found 

 in Epping Forest, it certainly merits a locality being given. Antirrhinum £latine is mentioned as 

 being common in ditches in the neighbourhood of Chigwell. By a ditch is generally meant an 

 excavation with water in it ; but the plant in question is foltnd almost exclusively in cultivated 



