236 



KNOWLEDGE 



[Jan. 13, 1882 



lungs ; tlio gills cithor disappearing when lunf^s appear (as in the 

 frogs, toailB, iinil newts) or persisting (us in jirotcus, the nxolotl, 

 <ic). Frogs unil other amphibians further differ from reptiles 

 in undergoing a metamorphosis during their development, und 

 in the want of seales or bony jilatcs on the skin.— Andrew 

 Wilson. [1 find what "I had always Bup|)o8ed " (viz., that the 

 class Reptilia included the Amphibia, and therefore the Batra- 

 chians) is an error. (It was not given, be it noticed, as 

 a reply.) I know, of course, thot sonio naturalists regard 

 the Amphibia and Heptilia as distinct clas.ies ; ond I see that in 

 I'rof. Newton's primer they are so given. I know also that Lin- 

 nicus's mistake in classing the abranchiate reptiles as amphibia 

 had been corrected. But there must have been some change in 

 classification of late, if that I mentioned has been definitely re- 

 jected ; for I find Prof. Owen, in " Brande's Dictionary of Science " 

 (1867), writing (1) under head "Reptilia," that those which retain 

 gills during a part of their existence are called Batrachians ; (2), 

 under head "Ampliibio," calling those which retain their gills 

 during the whole of their existence peribranchiate reptiles ; and 

 (3), defining Batrachia as "an order of Reptilia, including all 

 reptiles which, like frogs and toads, have naked skins and external 

 branchiae in the early stage of existence." — Ed.] 



[155] — I have known of a tortoise living ten years ; but I should 

 say the duration of life is longer, especially in the larger species. 

 I should imagine they do not remain " under the earth," in ordi- 

 nary circumstances, longer than the winter or cold season. — 

 Andkew Wilson. 



[157] — Aluminium. — Any good Chemistry, as Fownes', or Watts', 

 or Hitler's, gives a full account. It is too much to expect in these 

 pages. Spell aluminium with two i's, and emphasize the " min." 

 — Lewis Akundel. 



[170]. — " E. M.," in Knowledge, for Jan. 6, thinks that the 

 existence of ])arasites in meat is an argument for vegetarianism. 

 Permit me to remind " E. M." that parasitically-infested meat is 

 not normal meat. If " E. M.," as a vegetarian, acquired a tape- 

 worm guest from a lettuce, he would not abjure his vegetable food, 

 I suppose, because of his liability to infestation therefrom, anymore 

 thaii he would cease drinking water because some waters contain 

 young flukes. The lesson taught by my paper is not the abjuration 

 of flesh as an article of food, but the careful selection of healthy 

 flesh; and, I will add, of healthy and normal food of all kinds — 

 vegetables and drinks included. The pros and cons of vegetarianism 

 lie quite outside your correspondent's letter and my article. — 

 Andrew Wilson. 



[180] — "An Amateur" inquires the "use "of bugs, fleas, flies, 

 and other "apparently useless insects." He should first learn that 

 ihe word " use" has a sole meaning and application (as he employs 

 it) to human life. Ho should learn next that each animal and 

 plant exists for its own sake, and independently of any " use " 

 which men may conceive it adapted to serve. Thus " An Amateur" 

 might as legitimately ask the use of seals, and might receive the 

 reply " to furnish sealskin jackets for ladies ; " and humming- 

 birds might similarly be regarded as existing for the purpose of 

 decorating ladies' hats. In a word, science can take no heed of 

 such a question as that put by " An Amateur." Like the Smith 

 of Perth, each animal and plant fights " for its own hand," and 

 lives and exists independently of all human ideas of use and no 

 use. — Andrew Wilson. 



!3[n6lDfr5 to Cori-fSponlirnts. 



* ^* All eommunicaHoiu Jbr tha Editor requiring early attention thould reach the 

 Office on or bffore the Saturday preceding the current ittuc of ExowLBDOB, <*« 

 \ncreanng circulation of ichich compel* ut to go to preii early in the veek. 



lllHTS TO CoBBKsl'ONDKNTS. — 1. Xo qucrtion» asking for ncientijic information 

 can be answered through the post. 2. Letters sent to the Editor for correspondents 

 cannot be forvarded ; nor can the names or addresses qf correspondents he given in 

 anncer to private inquiries. 3. JV*o queries or replies savouring tf the nature qf 

 advertisements can be inserted. 4. Letters, queries, and replies are inserted, unless 

 contrary to RuU 3, free of charge. 6. Correspondents should vrite on one side 

 only of the paper, and put dravings on a separate /*n/". 6. Each Utter, query, or 

 reply should nare a title, and in replying to letters or queries, r^erence should be 

 made to the number of Utter or query, the page on vhich it appears, and it* titU. 



W. A. C. Mr. Hutton points out that if we cease to eat meat we 

 shall destroy animals more certainly and more cruelly than at 

 present, by leaving them no vegetable food j and ho is an anti- 

 vivisectionist of the most pronounced type. We had better not 

 insert your objections to the toad-pressing story, lest boys should 

 try the very experiments you say the story suggests — which cer- 

 tainly would not have occurred to us. — A. St. Clair. We know 

 of no French educational paper whose editor woald take English 



stamps in payment. — W. H. H. Soamks. Certainly the i;i i. 

 occults the planets. Such phenomena' are announced ir. 

 " Nautical Almanac." The outer satellite of Jupiter often | :.-, - 

 considerably above or below the planet. In an article we wrote 

 in 18G7 for the Popular Science Rei'iew, we discussed the question 

 fully. — Fred. Blackett. Our price is small, our modesty great; 

 beyond sending sjjecimen copy, we would not force ourselves on 

 your society's notice. — W. R. Bland. The proprietors consider 

 that Buch notice should appear as an advertisement. — W. H. 

 Pertwee. Arctic explorers want, 1 suppose, to find what there 

 is at the Pole — land or water, greater cold or less cold, and so 

 forth. As to the other question, evolntionists may or may not 

 believe in the statement you refer to, or some of them may and 

 some may not; it is no business of ours. If you hod asked me 

 what I believed on that or kindred subjects, I might have replied 

 that it was no business of yours, which, though it would have 

 sounded abrupt, implies something which may be usefully 

 remembered. A man says he believes a certain scientific fact, 

 and he is asked — without rhyme or reason — whether, so 

 believing, he can believe something else which the inquirer 

 says he and others regard as a truth of religion. What 

 sensible answer can he make to a question so absurd, with- 

 out being somewhat plain-spoken ? To such a question, as to 

 my belief, asked me in public at New York in 1874, 1 answered, " My 

 belief is that there is a deal of nonsense in the world," and 1 believe 

 still that I could not have answered the question more precisely, 

 unless for " nonsense " I had used a stronger exjiression.— 

 Frank R. Thomas. It certainly appears that " the mind ia only 

 partially active, and that the sounder part of it — the reason — is 

 dormant when we are dreaming." You ask, '"to what does this 

 point ?" We are not quite sure that we understand you. It seems 

 to us what might very natural!}' be expected. — E. H. Thanks for 

 pointing out that Newton, in his work on fluxions, descril>ed the 

 Witch of Agnesi, calling it a " eonchoidal." We agree with you 

 that the curve cannot properly be called a qnadratrix. — F. 

 Wilson. The laws of perspective are purely geometrical, and 

 the slightest acquaintance with geometry would show you that 

 perspective cannot possibly account for the disappearance of a 

 hull of a ship before its masts. The hull is unseen because there 

 is something in the way, namely, the rotundity of the earth. — 

 Wm. H. Allen. Thanks for extract on actinium. VeryliUleis 

 known yet respecting the properties of the new element. Several 

 have been discovered since spectroscopic analysis was invented. — 

 Desideratum. The delay you refer to is explained by the circnm- 

 stance that we receive so many letters like the one signed " De- 

 sideratum." — A. CnAMPNES.>;. We cannot reply by letter to queries, 

 even when a stamped and dii-ected envelope is sent. — An Ixquiher. 

 If we put in your query about cats falling on their feet, we shall 

 have all our school-boy readers trying experiments — applying the 

 inductive method, with projective illustrations. — .^^OLUs. No; the 

 Americans do not (we believe) " fire their storms at us out of a 

 gun." Ships reaching America give news of storms travelling 

 eastward across the Atlantic, which had been already traced 

 across part of the American continent. The prediction is based 

 on the belief that such storms will travel farther east before they 

 die out. Y'oii are more correct as to solar heat being the cause of 

 storms ; but they may arise without the sun being " in some 

 vagaries." The heat he pours on the earth is tolerably constant.— 

 One who wants Knowledge asks for information respecting the 

 mantifacture of Portland cement, or titles of books relating 

 thereto. — E. S. We have not room for your letter on primary 

 colours. If a definition of primiuy colours were given, which 

 should carefully distinguish what is physical in the matter from 

 what is physiological, we might get more satisfactory statements. 

 As to your questions relating to religion, I reply that to exclude 

 religion, in its wider and nobler sense, from our columns would 

 be to exclude science. But dogmatic religion we cannot away 

 with. One might as reasonably speak of a Mussulman spectro- 

 scope, or of Brahminical hydrogen, as of Christian science. Science 

 is neither Christian nor un-Christian, but extra-Cliristian. We do 

 not want such matters to be treated in a calm, philosophic spirit, 

 but simply left altogether untouched. They have no proper place 

 here. As a mere matter of detail, we may note that they never 

 are treated in a calm, philosophic spirit, perhaps because no 

 calmly philosophic person would be so unwise as to treat of them, 

 at all. — Dai.eth. About comets' nuclei later. — Mercury. For 

 names of Mr. Wallace's books apply to Messrs. Macmillan. They 

 will well repay study. Read also Dai-win's " Origin of Species" 

 and " Descent of Man." — Mabel. W. Laing recommends " E. H." 

 to read Dr. J. Reade's " Experimental Outlines for a Now Theory 

 of Colours, Light, and Vision," 1818, and W. Crum's "Experi- 

 mental Inquiry into the Number and Properties of the Primary 

 Colours," 1830 (books entirely out of date) ; also, if be reads 

 Dutch, N. Folmer's " Alpha van het Alphabet der Klenren," 



