296 



NA TURE 



[July 26, 1S94 



of Richard Jefferies, is very much abroad just now. 

 Sometimes he is more poet than naturalist, but he is 

 always a lover of nature, and though his interpretations 

 are often lacking in scientific accuracy, his observations 

 are generally worth putting on record. Dr. .Abbott 

 belongs to this class of nature's disciples. Systematic 

 science has no charms for him. He prefers rather to 

 roam the fields and woods, and watch life in all its vary- 

 ing moods and motions. Ensconced in the branches of a 

 high tree, he has seen sights never vouchsafed to mortals 

 with more limited horizons. He has watched the build- 

 ing of nests, and his observations on the method of work- 

 ing are as valuable as they are interesting. The foot- 

 prints of various birds, the sinuous traces made by 

 mussels and water-snakes on the ripple-washed sand of 

 a sea-shore, and an infinite variety of similar im- 

 pressions, have furnished him with objects of study. 

 These are the kind of topics treated in the book, the 

 scene of which, judging from internal evidence, is in 

 Maryland. For the most part, the reading is plea- 

 sant'gossip, free from rhapsody and tiresome platitude. 

 The title does not, however, clearly express the character 

 of the contents, for it only refers to one of the seventeen 

 papers which make up the volume. 



The publishers are famed for their tasteful editions in 

 belles-lettres, and they have done their best to give an 

 esthetic value to Dr. Abbott's musings on sundry 

 phenomena. 



LETTERS TO THE EDITOR. 



[The Editor aofs not hold hinnet/ resfionuble for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with )he writers of, rejected 

 manuscripts intended for this or any other part o/Naturb. 

 No notice is taken of anonymous comnunicatio>is.] 



The Electrification of Air. 



As attention is called to this subject by the paper, by Lord 

 Kelvin and Mr. Magnus Maclean, in Nature for July 19 (p. 2S0), 

 it may be worth while to point out that two distinct questions, 

 which it is important should not be confused, arise as to the 

 electrification of air. The first question is whelher an electric 

 charge can be given to a quantity ofdust-free air? In other words, 

 whelher a gas can get into a condition in which it can carry a 

 charge of electricity ? The evidence derived from the electrifica- 

 tion obser\cd in vacuum tubes, &c., seems almost conclusive in 

 favour of an affirmative answer to this question, which is the one 

 considered by Lord Kelvin. The second and quite different ques- 

 tion is whelher this electrification of the gas is possible unless 

 same of the gas is in a special state, such, for example, as would 

 l>e produced if some of the molecules were split up into atoms ? 

 To adopt a definite theory, for the sake of pulling the question 

 clearly ; Is the electricity in the charged gas carried by molecules 

 or atoms ? 



It was the second of these questions, not the first, which I dis- 

 cussed in my " Recent Researches in Electricity and Mag- 

 netism," under the heading "Can a molecule of a gas be 

 clearified?" The ultimate fate of a charged drop of water, 

 alluded to by Lord Kelvin and Prof Elihu Thomson, is, as far 

 as I can sec, not in any way inconsistent with the view which I 

 advocated, that the molecule of a gas can not be electrified. For 

 take the case of a drop of water impure enough to be regarded 

 as an eleclrolytc, and suppose it negatively electrified. The 

 negative charge will lie carried by oxygen ions or atoms ; thus, 

 if it were possible to cvajiorate all the walcr aw,ay, the electricity 

 would be left on these atoms, and there would be no charge on 

 either the molecules of water or air. On the other hand, ihc fact 

 that the water mrjlccules escape from the electrified surface 

 without any electrification, seems in favour of the view that the 

 water molecutci can not be electrified. Again, it is worth 

 rememb-rrinc; that a square centimetre of surface, immersed in air 

 at tl. ! temperature and pressure, is struck by about 



10'' per secon 1 ; yet such a surface will retain for 



hour,, will nit scosible loss, a charge of electricity, which, as we 

 kaow from the electrolytic properties of liquids and gases, could 



NO. I 29 I, VOL. 50] 



be cirried by a few thousand millions of particles if these were 

 to receive such a charge as the atoms of the gas are able to 

 carry. J. J. Thomson. 



Cambridge, July 20. 



"Testacella Haliotoidea," Drap. 



In Nature for the 5th inst. Mr. J. Lloyd- Hozward has a 

 note headed "Testacella haliotoidea," of which slug he says 

 that "specimens are not infrequently collected in asparagus- 

 beds, as are also those of the much rarer T. sciiluhnn." 



It will be allowed that the latter specie> is often found in 

 such places, those recently recorded from Buckhurst Hill, for 

 instance (Essex NaluralisI, vol. vii. 1S93, p. 46), but excep- 

 tion may be taken to the statement that Testacella sen I ul urn, 

 .Sow., is much rarer than Testacella haliotoidea, Drap. — in fact, 

 it would seem that the opposite is the case. 



Until recently every British example of the genus not refer- 

 able to Testacella maugei, Fi-r., was called haliotoidea : however, 

 the late Mr. Charles Ashford in 18S5 pointed out to Mr. J. \V. 

 Taylor that there were anatomical differences between the form 

 that seventy years before had been called .ti «/«/«;» by Sowerby, 

 and the typical haliotoidea. The figures in Mr. Taylor's paper 

 (Journal of Concholog)', 1S8S, p. 337), which was the outcome of 

 this, were not altogether convincing, and the present writer, in 

 some remarks to the Linnean Society (June 1S93), on the 

 method of feeding in Sowerby 's species (see Zoolos^ist, Augus' 

 1893) thought it advisable to endorse Mr. Taylor's statemenl- 

 from his own observations. Again, in the following July, Mr. 

 Walter E. CoUinge (.Annals and Magazine of Xalural History') 

 gave some very clear figures and descriptions of some 

 anatomical details of the genus, ably supplementing Mr. Ash- 

 ford's work. 



Now that the specific distinctness of Testacella scutulnm i~ 

 beginning to be recognised, the records for this species arc 

 getting numerous, while those for haliotoidea are apparently 

 dwindling, doubt being thrown on existing records, and, as can 

 easily be foreseen, supposed localities having to be struck 

 out in favour of the allied form, .\lmost all the shells of this 

 genus preserved in the British Collection at South Kensington, 

 on running through them with Mr. Edgar Smith, turned out to 

 belong to Testacella scutulum. 



Mr. Bozward's record of Testaulla haliotoidea is interesting, 

 as Tate's list of counties can hardly be reliable now, a citalogue 

 of localities as exhaustive as that given for the other species by 

 Mr. Taylor, in his paper, already referred to, would be most 

 useful. The following are a few records which the writer has 

 been able to lay his hand-; upon, at short notice, for the true 

 haliotoidea. 



Horsham. — The first specimen which Mr. Taylor sent to Mr 

 Ashford, which was really this species, was from her. 

 (letter to the writer). 

 Oxiord. — Mr. Taylor mentions having a specimen from Prof. 



Poulton (in his paper on T. scutulum). 

 Chepstow. — Mr. Taylor mentions this locality (letter to the 



writer). 

 Yorkshire and Cornwall. —Mr. CoUinge had his specimens 



chiefly from these counties (letter to the writer). 

 Ireland. — Ur. Scharff gives Youghal, co. Cork (in "Irish 

 Land and Freshwater Mollusca," Irish A'aluralist, 

 1892). 

 Kew. — The writer collected specimens in the Royal Gardens 

 some years ago. Wilfred Mark \Vi-:iiii. 



Biological Laboratory, Chelmsford, July 19. 



Two Arctic Expeditions in One Day. 



The 7th of July was memorable as the date of sailing of two 

 Arctic expeditions, one from St. John's, Newfoundland, the 

 other from New York. The steamer Falcon, having set out from 

 New York in June, and touched at St. John's.madc its final de- 

 parture from that point for Bowdoin Bay, Inglefield Ciulf, 

 Greenland, having on board the Peary auxiliary expedition, 

 the intention being to convey Lieut. Peary and his twelve com- 

 panions b.ack to the United States in Septemlicr, after their 

 twelve months' sojourn in the Arctic regions. The Falcon was 

 saluted in passing by the British man-of-war Cleopatra. 



The expedition will be gone about ten weeks. Cary Island, 

 Cape York, and Clarence Head will be visited. Various 



