Sept. 29, 1882. 



♦ KNO\VLEDGE 



301 



send a sketch, however rongh, showing how the pipe and flap are 

 situated ? — P. H. M. wishes to know how best to polish stones for geo- 

 logical spocimens, — W. H. S. Taking yonr postsci-ipt first, in which 

 yon express some anxiety lest I should "sit upon" your letter, my 

 answer must be akin to that of the Cherubs, when the polite 

 French saint on whom they had called said, " Asseyez-vous, 

 mexdcurii." " Nous n'avons pas de quoi, monsieur," was their reply. 

 In like manner I find nothing to sit upon in your letter ; on the 

 contrary, I find it very kindly, courteous, and considerate. The 

 difficulty about supplements on special subjects is that they would 

 have to be high-priced, as the number of specialists is small. From 

 a rough calculation I find that for a thousand astronomical readers 

 a supplement of 16 pp. would have to be priced at 4d. at least. 

 After all, the purpose of Knowledge is rather to encourage general 

 than special study of science. We want our specially astronomical 

 readers to enjoy our papers on subjects botanical, zoological, elec- 

 trical, chemical, &c., and so with other subjects. I suppose the pro- 

 fessed botanist would hardly expect to learn much that was new to 

 him from one of Mr. Grant Allen's charming papers, though I hope 

 (for his own sake) that his special study of botany would not deprive 

 those papers of the charm which they have for those who, like 

 myself, have only a general knowledge about botanical matters. 

 So again, though I hope that professed students of astronomy 

 may find something to interest them in my lighter essays on astro- 

 nomical matters, 1 do not write for them, but to interest, as far as 

 I can, those who are not astronomers. — J. H. Cobbett (representing 

 four others), L. K. MooRso.\t, R. Prothero, Fixe Weatbkr, 

 Meagles, H. H. Taylor, and others, in great number decide 

 against the Weather Charts ; Ja.s. Wilson, Jl'n., JI. Hartington, 

 and a few others, like the charts, but are not disposed to insist on 

 them ; Meteorologist must have them. " Must he ? " If the 

 majority decide against them, " let him not hope to have 

 them."— M. R. I really must set that Top Spinning. (No 

 occasion to explain that you " did not mean your severity." 

 I read "fun" in the first line. " Cupidus Cognoscere" is re- 

 ferred by M. R. to Ferguson's Select Mechanical Exercises. — 

 B. M. Well, I must confess I think with Tyndall and Huxley 

 that many anti-Vivisectionists are fanatics. But who ever called 

 them " bestial " ? " Bestiarian " is a very different thing ; it is a 

 term no anti-Vivisectionist should be ashamed to accept. In fact, 

 moderate as my own views are, I should call myself a Bestiarian in 

 Owen's sense. You think I do myself injustice in saying that I 

 have nothing to do with the atrocities of some Continental Vivi- 

 sectionists. Would yon think, if I said I had nothing to do with 

 atrocities described in the daily papers, that I should be suspected 

 of applauding them ? — Newton Crosland. Hampden and Parallax 

 no more consider tlieir arguments refuted than you judge yours to 

 be. I fear the distinction yon draw between yourself and others of 

 the heterodox is not gcncnilly recognised. — Rerry Rix. Snch sug- 

 gestions as yours (and so made), are really useful to an editor. I 

 think the subject you name (spectroscopic analy.sia), one which 

 specially requires treatment in such a journal as this. I thank you, 

 and by no means complain as of the grumbling few. — A Critic. 

 All egotism is silly. Why pile up epilliets ? One would almost 

 imagine you were angry ! Now, you are not egotistic ; for yon 

 write rude things, on a post-card, anonymously ; which means 

 that you would rather know yourself contemptible than be so known 

 to others. Being altogether above egotism, you should only pity, not 

 abuse, those who still have some respect left for themsel ves. Not every 

 one can go, as you do, beyond Mawworm, who only liked to be de- 

 spised, whereas you evidently like to despise yourself. For 

 portrait, see Punch, p. 123, current vol. — Ebkn. Jones. Transit 

 of Venus now fairly begun. Agree with you about the weather 

 Charts ; but if you only knew how we were entreated to have them, 

 you would understand. — F. C. I trust the dyspepsia for which you 

 want a remedy has not been caused by your " reading our answers 

 to correspondents this last six months." By-the-way, I see it was 

 not, as you go on to mention that it has lasted eighteen months. I 

 doubt if even our medical contributors would venture to suggest a 

 remedy for an ailment of such long standing, without much fuller 

 particulars, and seeing you personally. — E. H. Lef.ney, H. J. Wat- 

 son, A. J. Cannot drop either Whist or Chess. — W. C. Thomas. 

 Many readers want the smaller type to be all but wholly disused. 



ELECTRICAL. 



Z. Y. X., thinking it may interest our readers, lias kindly .<!ent lo 

 say that while in Brighton a few weeks ago there was exhibiting 

 there " an electric boy ; he gives an electric shock to anyone who 

 touches him, and walks about so that he can bo examined. The 

 exhibitors state that he was bom in Australia, of English parents, 

 and lias been exhibited there, as well as in Now Zealand and the 

 United States; that ho began to show extraordinary electrical 

 powers after his fifth year, which increased with his age ; that lio 



had good health and wonderful curative powers in cases of 

 neuralgia, rheumatism, and headache." I do not remember having 

 seen or heard anything of this marvel, and should be very careful 

 to ascertain that there was actually no deception being attempted. 

 Such a thing might easily be done. I should like to hear more of 

 this. — Henry MacEwen. Urquhart's "Electric Light" is pub- 

 lished by Messrs. Crosby, Loekwood, and Co. It does not give 

 much of the information you require, but his " Electrical Engineer- 

 ing" will doubtless supply it. The book, however, is not yet 

 published.— Henry Edmonds, saying that he knows nothing of 

 electricity, asks for the name of a good initiatory text-book. I am 

 afraid that unless he has the means of seeing or working experi- 

 ments, his progress will be more apparent than real. He cannot do 

 better than start with Angell's " Electricity" (Collins' series) and 

 Dcschanol's "Electricity and Magnetism." — C. B. In practice 

 the terms " intensity" and " quantity" are still, and will doubtless 

 for some time continne to be, freely used. The names or terms 

 may be in themselves "remnants of an erroneous theory" con- 

 cerning the nature and propagation of electricity, but they have 

 still the same significance as regards the -properties, or working 

 capacities, of a current. The term "intensity " is synonymous with 

 " Electro-motive force " and "quantity" with "current-strength." 

 The question is being more fully dealt with in the articles on 

 " Electrical Measurement" (see Knowledge, Nos. and 41), and 

 I think a perusal of them will be much more efficacious than a 

 restricted answer to a query could possibly be. Reference might 

 also be made to previous " answers " appearing in previous Nos. 



Letters Received.— G. Carid. — H. F. — C. Francis. — W. Davies. 

 — E.R. Cowley.— T. P.— A. Stradling.-Pleni Almoni.— E. P. W.— 

 A. N. S.— Hack.— W. B. Bishop.— X. Z.— Brynm.— A Perplexed 

 Student. — H. H. French. — S. Lawther.— W. Moon. — Abstainer. — 

 Stanley Baldwin.— W. S.— Leander.— No Alcohol.— Z. Y. X.— 

 Iota.— J. Glover.— J. Watson.— Yale Yrneh Rulitra.— C. C. C. C— 

 J. Eraser.— E. Holloway.— G. Henslow.— C. H. Romanes.— E. D.— 

 A. Gorham.— W. N. Bell.— E. S. B.-J. M. G.— J. A. Ollard.— G. 

 Kamensky. — Sufferer. — Indicus. — W. Hicks.— A. R. Woods. — 

 T. D. N. M.— A. Bray.— M. B. A.- Mangier.— H. McKendrich.— 

 G. Glasgow.— C. J. Eve.— C. Pool.— J. Huddlestone.— W. H. Ruth. 

 — H. A. Bulley.— L. R. L.— M. A. Close.— A. W. D.— It. M.— 

 W. P. H.— A. A. Murdoch.— J. B.— F. Lobritz.— J. J. Rostri.— 

 J. S.— R. Leigh.— B. M.— A. P. S.— Hallyard. Others received 

 since Monday. 



EUEorEAX Postac.e. — A recent article in the Deutsche Industrie 

 Zeitumj, on the European postal traffic of 1880, shows that the total 

 number of articles sent was 6,200,577,592. Letters and postal cards 

 were in the proportion of 013 per cent. ; newspapers, 229 ; book- 

 packets and patterns, 15-8. England was first, with 272 per cent, 

 of the whole ; Germany second, with 233 per cent. ; France third, 

 with 196 per cent. Nearly everywhere there is an increase of 

 letters and postal cards per head of the population. An estimate 

 shows that in England each inhabitant allows ten days between t\yo 

 letters ; in Switzerland, two weeks ; in Germany, twenty days ; in 

 Russia, two hundred and eighty days ; in Bulgaria, about three 

 years. There were 55,479 post-offices in 1880, an average of one to 

 every 5,8599 inhabitants. The emploin's numbered 250,665. The 

 postal traffic has increased 58-8 per cent, in eight years, and in the 

 whole of Europe the surplus is about f27,O0O,O0O. 



INFLL-ENCE OF CoERCIVE FoRCK ON THE HeAT PrODUCTB BT 



Magnetisation. — Mr. L. Pillenx has made some experiments from 

 which ho concludes that magnetisation produces great heat in 

 paramagnetic metals. In order to obtain a marked effect, ho 

 magnetised and demagnetised iron and steel cores at short inter- 

 vals by means of a Do Mi'riten's alternate current machine. In 

 this way he succeeded in raising the temperature of an iron core 

 to at least 300* C. Ho states that a piece of pure tin brought 

 into contact with the heated core melted instantaneously. 

 Replacing the iron core by cores of copper, brn.os, and tin, llr. 

 Pillcux found that their temperature remained unaltered. Using n 

 steel core, he found the heat considerably greater than in the case of 

 the iron core. In the case of a very soft iron core the temperature 

 was still less, and when using a core consisting of a bundle of very 

 soft iron wire the temperature showed a further ilccrea.'Je. From 

 his experiments Mr. Pilleux concluded, first, that the heating of tho 

 cores of electro-magnets must be attributed to magnetisation and 

 not to induced currents; and second, that the coercive force of tho 

 cores increases their propensity for becoming heated in tho same 

 manner as the resistance of a wire causes its tempcmturo to bo 

 raised by the passage of an electric current through it.— La Lumiere 

 Electrique. 



