212 



KNOWLEDGE 



[Jan. 6, 1882. 



[141]— Time or Glacial Erocn.— Tliie querist need not trouble 

 liiniBcIf about any othifr theories than Croll's. There are others, 

 however, uiiil if he is ambitious of wasting some valuable time ho 

 may read Col. Drayson's " Ijist Glacial Epoch." — Pacocl. 



Namks of STAB.S. — In reference to letter 127, paffo 143, 

 there is no work in Gn^tlish on the names of the stars. There is 

 one in German, by a writer named Ideler, and is called " Ueber 

 den Ursprunp; nnd die Bedeutun« der Sternnamen " — " On the 

 Origin and Sijjnitication of Starnames." It is a pity that there is 

 no translation of this work into Enjflish. Of the great interest 

 scientific, archa-ological, and poetic, attaching to the names of stars, 

 there surely can be no question. — Zkta. 



Weathek Gi'iiiE. — (Page 128). Allow me to mention that 

 Messrs. Routledge publish just such a guide, entitled " A Manual 

 of Wcathcrcasts," Is.— Euptebis. 



9[nstorr£{ to CoiTtspontinits. 



•,• All communifatitmM for iKt Editor requiring tarlg atttniion thould reach tht 

 Office on or h^ore Ike Saturday preceding the curreiU issue of EsoWLZDOB, <A« 

 inrrearing circulation o/ tchieh compel* ne to go to pre" early in the «eek, 



UlsTS TO CORBESPOSDESTS.— 1. Xo qiteitiont asking /or scientific information 

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

 cannot be fonearded ; nor can the names or addresses (f correspondents be given in 

 ansKcr to private inquiries. 3. -Vo queries or replies savouring of the nature qf 

 advcrlisemcnts can be inserted, -i. Lctttrs, queries, and replies are inserted, unless 

 contrary to RuU 3, free of charge. 5. Correspondents should irrite on one side 

 only of the paper, and put drawings on a separate let^f. 6. Ea^h letter, query, or 

 repUf should kate a title, and in replying to letters or queries, reference should be 

 wtade tothe nunler of letter or query , the page on which it appears, and its title. 



K,^Y. Your 8nf,'gestion, that ladies should meet for discussion of 

 matters scientific, educational, phrenological, and physiological, 

 instead of tea and small talk, is no doubt excellent ; but our 

 space is too crowded for the in.'^ertion of your remarks in full. — 

 Zarks. We agree with you that all paradoxes should not be 

 omitted from a paper like the jiresent. We propose to act in 

 accordance with that view. — T. Pkeston Batteksbye. From 

 some of my published essays, you will see I take great interest 

 in the pheuomena of mesmerism : I would like much to see 

 your papers. — W. A. C. What we said about vivisection was 

 very moderate. We, of course, have nothing to say to the 

 change of law, which you suggest as logical. If you 

 had ever known the torture of one dear to you 

 alleviated through knowledge accjuired from such experiments 

 as you denounce, you would possibly see that the question 

 has two sides to it. — O.ne I.ntekested ix Science. Heat 

 waves and light waves are of the same nature, and both travel 

 through the ether. JIany light waves are heat waves, and rice 

 i-ersi. Your second question belongs to a region outside of 

 knowledge. The gratings referred to by Prof. C. A. Young, are 

 what are called refraction gratings, in reality, series of fine 

 parallel lines cut on glass very close together. The formation of 

 a spectrum by means of such a grating requires a fuller explana- 

 tion than we can give here. A collimator is a portion of the 

 spectroscopic apj>aratus by wliich the rays are made parallel 

 before entering tlie spectroscope proper. — Gcs'. The dimensions 

 of space may be described as length, breadth, and depth. In a 

 plane wo have only two dimensions, length and breadth. Some 

 geometers think they can imagine the possibility of a fourth 

 dimension. When they can show us that a point may be neither 

 in a piano nor out of it, we may begin to think with them. — 

 W. WiLSo.v, M.A. Is it not purely a question of words? 

 You would say, wo seo the light that comes from an 

 object ; others would say (and, I think, rather more 

 correctly) that wo seo the object by means of the light. — Hexky 

 Wkntworth JIo.nk. You suppose I " have not forgotten pub- 

 lishing" for you" in the English J/cc/innic about nine years ago ;" 

 1 remember writing a short notice in the Paradox Column of your 

 theory of Re-Cre,ation, but "publishing" for you would have been 

 a different matter. I have read your letters headed " The God of 

 Israel" and "The Lord of Hosts" in the Jewish World. Thanks 

 for sending the paper to me ; but the letters are hardly suited for 

 notice in these columns. — F. P. No ; at least that was not the 

 name given. Sleep preventatives are not safe. Drowsiness 

 (unless following after too heavy a meal, tho use of stimulants, 

 opiates, and tho like), means that rest is needed, and that, there- 

 fore, rest should be taken. Your other (jucry would hardly be 

 understood. Even Dr. Andrew Wilson could not, off-hand, tell 

 you tho name, origin, and habits of creatures about which you 

 only say that they are minute, have developed themselves 

 recently within your aquarium, are white, have numerous legs, 

 and dart through the water with a jerky, spasmodic movement, 

 some of them carrying what you suppose to be their young upon 



their backs. But if yon were to describe briefly the original con- 

 tents of your aquarium, give the exact number of legu, and state 

 something definite as to the size and shape of the small white 

 creatures, yourquery should appear. — Uaeky Whate.h. We should 

 have to insert rejoinders if your article were published. We have 

 definitely stated more than once that onr subject is science, and 

 that in theso pages the religious doctrines of no sect whatever shaU 

 be either attacked or defended. — E. Bl'Rke. Declined with thanks; 

 no space. — R.T. Thanks; but we ought not to insert what amoimta 

 in fact to a definite advertisement of the books named. Cause 

 of curved shape of rainbow has been explained in recent nnmben. 

 Along lines inclined at a certain angle to the line from sun 

 to observer (they make an acute angle with this line produced) 

 come the rays giving, after internal reflexion in rain drops, each 

 particular colour. Therefore, the rainbow arc of that colour is ft 

 circle on the sky, having the point directly opposite the snn 

 (with reference to the observer) as its centre. Loomis'e 

 " Treatise on Practical Astronomy " is, we believe, to be obtained 

 of Triibner, if not jmblished by them. Its y>rice is Ss. or 8s. 6d. 

 — W. B. KcssELL. The promised paper on the subject of moon's 

 former proximit}' to the earth shall presently appear. (The 

 moon was not i)rojected from the earth, according either to this 

 theory or to any other regarded as admissible by science.) 

 Xo. 7 can still be obtained from the publishers. — Toper. Your 

 question is vague. You can get a useful knowledge of the 

 elements of astronomy with the time yon mention as at your 

 disposal, if you use it well. But the books you have are not very 

 well suited for your purpose. Herschel is too diflicult. and the 

 " Elementary Lessons " (though written by one who has done 

 excellent work in some departments of astronomy) has too 

 many errors in it to be of much use, unless, indeed, yon 

 could get from Appleton's, New York, the American edition, 

 in which the errors arising from the author's want of familiarity 

 %vith mathematical and theoretical astronomy have been corrected. 

 — Excelsior. We thoroughly agree with yon, though we have no 

 room for 3'our letter. Whipping means, in ninety-nine cases out of 

 a hundred, laziness and bad temper on the teacher's part ; where 

 the teacher is also a parent, you may say a hundred instead of 

 ninety-nine. — Amiccs Scienti.e. We have already reprinted back 

 numbers, but third editions are rather costly affairs. — M. J. H. 

 As a rule, extra outlay for larger size telescope will repay. Few 

 ever buy a telescope who do not before lung wish they had bought 

 a larger one. I would advise yon to get the largest and best yon can 

 afford. Such an instrument as you describe would do a great 

 deal of interesting work for you, if the object-glass is by a good 

 maker. The question about nebula; and double stars is vague. 

 Every telescope will show some double stars, and give interesting 

 views of some nebute. See answer to "Amicus Scicntise" as to 

 back numbers. — J. C. Lloyd. The constellations revolve around 

 the pole, the pole itself remaining unchanged in position. The 

 pole-star revolves in a small c'lrcle around the pole. — M. M., alias 

 J. H. Have we not requested that yon would put outside your 

 letters an address to which they may be returned ? Did you think 

 we were blind, that we should not see through so thin a disgnise ':* 

 — W. StoTT. Mr. Allen shows that where such and such qualities 

 appear, such and such results follow. If the results you suggest 

 followed from the silveriness of whitebait, natural selection wonld 

 cause the species to become less silvery, generation after gene- 

 ration. But doubtless the colour is protective. In what yon 

 suggest as to creatures animate or inanimate having anything 

 to do with the matter, of their own will, you are, of course, 

 joking. — William Fredericks. Is there a bump of spelling in 

 your phrenological system ? Or are we to suppose that the 

 " prooff" and "infamation" you require are some articles 

 of which we have not yet heard ? We have not asserted 

 that "to term a system a science it must have adherents 

 among men of science," because that needs no assertion, and 

 requires no proof. To be scientific, a system must be able to bear 

 scientific tests. — J. Baretz. You say, amongst other remarkable 

 things, that the celebrated Courvoisier was a great admirer of 

 Gall and Spurzheim : surely you must mean Corvisart. Cour- 

 voisier was a murderer. — W.B.G. You arc right, but the fact is 

 pretty well known that Archimedes showed tho sphere and cir- 

 cumscribing cylinder to have equal cur\-ed areas, as a iircliminary 

 to establishing the relation between their volumes. It has never 

 yet been shown that the ir relation in the great pyramid should 

 replace that given by Herodotus as the one determining the 

 pyramid's height — namely, that surface of each face is equal to 

 si|uare on diameter. The pyramid fulfils this quite as closely as 

 the other. — Cosmos. Wo sympathise with your views ; but we have 

 to combine several quaUties in oixler to appeal to as many as pos- 

 sible. — W. .Cave T. Longmans, Chatto A Windus, and Smith, 

 Elder, & Co. — S. E. O'Dell. Xo, sir. We are obliged to you, but 

 desire no continued articles in favour of phrenology, or against t 



