Ja 



1882.J 



KNOWLEDGE 



13 



anstong til Corrrsfponlifntsf. 



*^JU cmmmteiiUons for ilu Editor requiring early attention ihould reach the 

 Oj!t» on or before the Saturdof preceding He current iuue of Kxcwtssei, the 

 i0i:rta*ing circulation of which eompele us to go to preet early in the veek. 



HlXTS TO CoHBBSPOXDE^rrs. — 1. Xo qneftiona atking for tcientijic information 

 can be anrieered through the post. 1. Lettera went to the Editor for correepondente 

 ctinnot be forwarded ; nor can the name* or addreeeet of correepondente be gicen in 

 answer to private inquiries. 3. Correspondents should write on one ride only of 

 the paper J and put dratcings on a separate leaj. 4. Each letter should hare a title, 

 and in replying to a letter, r^erence should be made to Us number, the page on 

 which it appears, and its title, 



J. Haetixgtox. You consider that with our present circulation 

 (»Thich yon under-rate, by-the-way, for our first volume Iiaa reached 

 niany more than the 20,000 you mention) we oufrht not to think of 

 increasing oar price. We do not think of so doin^. But we think it 

 probable you form inadequate ideas of the relation between the 

 expenses and the returns of such a journal as this. You speak of 

 20,000 twopences ; at trade rates 20,000 pence would be very much 

 nearer the mark. These are sordid considerations, are they not ? 

 why, certainly ; and the thought of daily mejOs is an animal thought, 

 is it not ? Try raising your sonl entirely above this animal thought 

 for a week or two, and then give us your ideas about Knowledge. — 

 UxiT.ts. Yes; the vibrating periods of the different rays of the 

 spectrum have been accurately determined. . The information will 

 be found in any treatise on the spectrum. There are 458 billions 

 of undulations per second in the extreme red, 727 billions in the 

 extreme violet. — Xemo. Those stories of marvellons eyesight have 

 often been found to be untrue. I should imagine Brussels paper of 

 1875 or 1876, from which you send an extract, appeared in the great 

 gooseberry season. Let telescopists judge:— It tells us that Jean 

 Trubell could see the four moons of Jupiter and the two rings of 

 .Saturn. Not a true bill, yon may be sure. — J. Gottfried. The 

 Magic Square, combined with the Knight's Tour, is good in its way ; 

 but we cannot find room for it. We want a plan for getting a quart 

 into a pint pot ; it always beats us. — Simplex. Slany thanks. — 

 W. W. Fah-cus. Your theory of lightning hardly consistent with the 

 production of the electric spark in perfectly dry air. — G. B. Fraseb. 

 I ought long since to have thanked you for the very interesting 

 book by Mr. Lindsay, which you have kindly lent me. It is full of 

 matter of great value to me. — J. S. J. Thanks for note on change 

 of colour of hair in case of one of the surrivors of Isandula. — 

 Thoughtful. Will find space if possible.— Corbeau. Yes; La 

 Fontaine's familmr fable makes the crow act rather foolishly. In 

 Chaucer's Xun's Priest's Tale, it is Chanticleer who is beguiled by 

 Keynard's flattery, and then Beynard is beguiled in turn. But this 

 itj a lesson in sense, not in scienjo, — to show us 



What it is for to be reekelcss. 

 And negligent, and trust on Battery ; 

 and also that he is 



Indiscreet of govei'nance, 

 That jangleth when that ho should hold his peace. 

 .^I'^sop's fable of the "Crow and the Pitcher" might be used the 

 other way, if fables counted. — Euclid. Thanks for account of fire- 

 ball on May 4 at 9.30 p ni. If the same object was seen by others 

 tar away from your station (Bolton), and a good account of the 

 apparent pith can be given, the observation may be useful in 

 determining the real path of the meteor in our air; otherwise not. — 

 Jas. S3IITII. There is no rigid arch, and practically no arch at all, 

 the curvature of the earth's superficial strata being so slight. If 

 the Uim.tlayas were twenty niiles high there would be some reason 

 for wondering at their stability. To all intents and purposes the 

 pressures existing within the earth are such as would result if the 

 whole earth were fluid. The cohesion even of a granite stratum, 

 of whatever thickness, small or great, does not prevent the whole 

 stratum from ]iressing downwards, and communicating downwards 

 the pressure it receives from above, with practically unchanged 

 effect. Sir W. Thomson's argument is, in fact, just this, that there 

 is no solid shell with fluid nucleus relieved by rigidity of such 

 shell from external pressure, but that the earth's whole globe is 

 continuous, with no freed fluid mass within. If yon consider that, 

 were the whole earth water, an ice mountain of any height (con- 

 sistent with the rigidity of ice) could rear itself above that fluid 

 surface, sustained by fluid pressures alone, you will see how little 

 force there is in the argument you derive from the llimalaya.s. 

 E. S. IxsULL, points out that in the Pharmacy Act, 18GS, prepara- 

 tions of morphine, as well as opium and all preparations of opium 

 are specifically mentioned as poisons. — F. "T. Jones. We would 

 print your thoughtfully-nTitten letter in full, were there space : but 

 there it not. The answer to your difficulty is simply, that within 

 the period covered by astronomical observation the day has altered 

 80 slightly that, until quite recently, it was regarded as conatont ; 



the slight change would not affect the appreciably unchanging 

 length of the year. You refer, I notice, to what I have stated as 

 the result of the investigations of others as if it were my own sijecial 

 statement. — J. U.vbgbeave. You ask in wliat sense the wordM 

 "moment of gravitation" as used by Dr. Siemens in his letter are 

 incorrect. In this — the word " moment," in all mechanical ques- 

 tions, means motion, not the force causing motion; Dr. Siemens 

 ajjplies it to mean the moving force on a mass of gaseous matter 

 at the solar poles ; a moving force is measured by the " momentum " 

 or '• moment," or quantity of motion it can generate, but 

 to the mathematician, calling a moving force moment is as 

 incorrect as it would be to call a printing-machine a printed 

 volume.— Some More Fellows. Why, certainly ; so I supposed. — 

 A. Jo.VES. — To deal with your problem, we must know the co- 

 efficient of elasticity between billiard-ball and cushion, and co- 

 efficient of friction between ball and baize. — Electbo.v. Others 

 think a great deal too much space given to that subject. — E. L. H. 

 Letter duly received, and shall appear. — E. M. O. Nay, but the 

 transit will soon be over. Comets come and go all the time. — 

 H. A. B. Sheet lightning is quite distinct from forked; the elec- 

 tricity is of small tension, and there is no thunder. A flash of 

 lightning being a discharge between cloud and earth, or between 

 cloud and cloud, can never be said to be dispersed in air. — F. T. 

 PiGGOTT. Paper on Foresights in type; thanks. Ale.x. Smith. 

 Surely a note to Mr. D. Bogue, publisher of the now defunct 

 Papular Science Review, would bring you what you require. — 

 Peccavi. Peccaristi — in this respect, that the ink you have used has 

 become so smeared that I cannot read all your questions. (1) A ray 

 of light appears to travel onwards without measurable diminution 

 within measurabledistances. (2) Do not knowexperimentally whether 

 ascending air bubble in water casts a shadow, though rarer than the 

 water. Theoretically it should, as a light ray will not pass out of 

 water into air at small angles. (3) Stanley's book on Fluids, reviewed 

 in K.nowledce a few weeks back, will help you as to the other ques- 

 tions, so far as I can guess their purport from the few nnobliterated 

 words. — F. W. Cory, F.M.S. I trj- a new arrangement for weather 

 this week. You say, in passing, that many readers probably " usurp 

 an Englishman's prerogative of grumbling — very often at nothing." 

 I would not mind that so much ; what troubles me is, that some 

 will grumble at evcr^-thing. This does not apply to your letter, 

 though you do describe the weather reports as " simply abominable." 

 I think you are about right ; hence the change. Possibly, «-ith the 

 first number of Yolume II., which opens in June, an improvement 

 on this may bo tried. Of course, there are many difficulties. — 

 R. M. Hands. The passage in the Pvramid points too far from the 

 Pole to aim at our present Pole Star, which is much nearer the Pole 

 than Alpha Draconis ever was or ever could be. — 3oVD Mos-<. Are 

 yon not thinking of a screw nearly " home," and overlooking the fact 

 that Sir E. Beckett's device is to help chiefly when the screw is " far 

 from home ? " He is no theoriser about such matters, bnt eminently 

 I>ractical. lam sorry I overlooked your astrononiical query. Will you 

 kindly repeat it ? — A. J. I. Thanks for story of omnibus horse stopping 

 when lady hailed unobser\-ant conductor, "it certainly suggests intelli- 

 gence and observation. — S. S. An intra-mercurial pl.inct, if such 

 exists, must bo very much smaller than Mercury, and being farther 

 off when in transit, would seem smaller still. It can readily Iw 

 shown that the largest intra-mercurial planet which can exist con- 

 sistently with the obser\-od constant absence of any naked-eye 

 object "during total eclipses, must be utterly invisible when in 

 transit (to unaided eyesight). — E. (!. I do not know of any com- 

 plete tables of logarithms giving remits to ten or twelve digits. — 

 Thomas Lvox.-i. Pray do not think us uncourteons in omitting your 

 querj- ; it is quite true that the term "knowledge" is very wide, but 

 the journal Knowledcf. is not very large, and something has to give 

 wav when an attempt is made to make the less enclose the greater. 

 " Five of Clubs " and " Mephisto " mil be proud of your favourable 

 opinion of their colnmns.— Sheffield. Thanks for your kindly 

 letter. Wo feel that, as yo\i say, it would l>o unfair to make n 

 change in the direction of "enlargement with increased price." — 

 Selexiai.. The keepers of second-hand Ixwk-stalls would bo able to 

 tell you where to get old copies of the examination questions for 

 matriculation at London. I do not know.— Fusiyama. .\1b', our 

 renders " will not away with " more magic squares ! How can your 

 lotus-leaf problem bo" donit with, without some data na to lotus- 

 leaves :■ — J. I.ITHER Hayxes. I do not know in what paper you 

 could get weekly information of the rainfall in Snrthe and Loin?.— 

 J. F. Description of microphone in hand, as pnimised ; but wiint 

 of space troubles us at present. " Eloctnm " and others wont more 

 clectricitv, and scarcely any n.sf ronomy ; "J. Hemming " and others 

 howl ngninst " Blow-pipe Chemistry," ond want more natural 

 histor^•; and soon all down the scientific subjwts.— J. Gbo,>.vexo« 

 Dawk! An index to Vol. I. will be issued immediately. 



[.Vboiit two pages of "Answers" hare been unavoidably held ever ] 



