362 



♦ KNONA/'LEDGE • 



[Fkb. 24, 1882. 



to Mi'teoritt'ii (of whii;li Mr. Vijftiolcii aponkii in Icttor 2C7. p. 302). 

 8<ini)* rcooiit pri'ti'iuiiMl iliHcuvoricH of foHKi) 8|M>iigc*R, comlH, unci 

 other fimiii) of /iioph} tli' life in MctcoritcH liiivc, IIioiikIi, Ikmih Hliown 

 conclunivoly to lie bnni-li-HH, (■xiitninntiuiiK of tlio muteoritcii nndor 

 tho miiu-roHcopo liuvin^' ili'moimtrntird tlio pnroly cryntallini' 

 ohnmi-tor of tho nllnKud orKimii' ninrkinKii. It in, on the wholv, 

 jUHt iiH well to Imvo ouu'h fiK*tii ri^lit boforo bediming to thf*ori/.o. 



I'robnbly Wnrtz's " Atomic Tlioory " (Vol. XXX. of the " Inter- 

 nntioniil Srionlilir SoricR") would be tho bi'Ht IkjoIc for " Krnodt 

 li. I.." ((picry 21!), p. 3(Ki) to obtnin ; it is tlio moHt recent one on 

 the Hiibjert. 



Mr. Siininierson (query 221, p. 303) scoms to bo uniiware that 

 there is nn exceedingly great tochnicnl difference between " Philo- 

 sophy " and " Natunil philosophy." Tho latter ia only another 

 word for what is now known as " Physics." Tho former has refer- 

 ence wholly to mental philosophy or metaphysics. With this pre- 

 liminary warning, I may say that Whowell's " History of the 

 Inilwctivo Sciences" is the mo.^t exhaustive work that I am ac- 

 quainted with on the subject. I believe that Miss Arabella Buckley 

 has comparatively recently written a more compendious book on the 

 History of Physical Science ; but I have at this instant forgotten 

 its exact title. Anything she docs is sure to be good. There is a 

 History of Science, too, by Mr. Rontledge, which I have seen, and 

 which, as far as I conid detcminc from dipping into it, seemed very 

 well dono. 



I presume that " G. R. W." (in query 227, p. 303), on the subject 

 of Harometric Oscillations, refers to a phenomenon with which I — 

 and I presume numy others— have long been familiar. The effect 

 to me of the oscillation of the mercury during a storm is irresistibly 

 suggestive of lirealhiiig. I have watched it on many occasions, and 

 the rhythmical rise and fall of its surface puts one at once in mind 

 of tho measured movement of the chest of a sleeping person. The 

 Editor's explanation of this is obviously the correct one. 



Doctress Kingsford (letter 276 p. 322), and some of her confreres 

 appear to misinterpret tho position which I have assumed towards 

 vegetarianism. I have never denied or disputed, for example, that 

 a severe course of City-feeding might Avith great advantage be fol- 

 lowed by a purely vegetable regimen, until the effects of over-eating 

 had passed away. Nor am I concerned to contest that individuals 

 may be so constituted as to thrive fairly well without eating meat 

 at all. What however I protest, and shall continue to protest 

 against, is the tone assumed by the " whole-hog" vegetarians. " I 

 wish," said an eminent statesman of the late Lord Macaulay, " I 

 wish that I were as cock-sure of anything, as Tom Macaulay is of 

 everything." It is this." cock-sure " demcanom- of tho phytophagists, 

 this blatant assertion that they m iiitt be right, and all the rest of tho 

 universe wrong, which is as irritating as it is unconvincing. As 

 a class, they are in reality as weak numerically as they are 

 intellectually ; but to read their publislied utterances one 

 would think that in mental capacity as in numbers they 

 infinitely surpassed tho remainder of their fellow mes (and 

 women). How (letter 277) a total exclusion of iiesh, 

 with the substitution of suitable vegetable products would 

 give me " yet better health " than, I am thankful to say, I in- 

 variably enjoy, 1 wholly fail to perceive. Moreover, when I regard 

 the potato-fed li-ishman, and see what his diet has brought him to, 

 or study the rice-eating Hijidoo, and note his slavishness and utter 

 pusillanimity, 1 do not derive much practical encouragement to 

 eschew fish and meat henceforth and for ever. One question I 

 should, in conclusion, like to have answered. I perpetually see the 

 names of Dr. B. W. Richardson and Sir Henry Thompson quoted 

 as strong advocates of vegetarianism. Now, my question is this. 

 Does either of these gentlemen restrict himself to vegetable food ? 

 Araprohat artijicem. " The proof of tho pudding is in tho eating." 

 It is useless to repeat with the clergyman of old tho anecdote, " Do 

 as 1 say, not as I do." If the two eminent men whom I have 

 named do not themselves practise what they preach, the pub- 

 lication of their testimony must, I venture to think, have a pre- 

 cisely opposite tendency to that hoped for, and intended by, those 

 who cite it. 



A few elementary considerations will enable R. W. I. (([uery 230, 

 p. 323), to answer his own questions. Actually at the North Polo 

 the diurnal circle of any heavenly body — assuming such body to 

 remain stationarj- in tho sky — is rigidly parallel to the horizon ; 

 the horizon in turn coinciding with tho celestial equator ("Tho 

 Equinoctial " of the maps and globes). Very well, then, neglect- 

 ing tho effect of refraction, it is quite obvious that as long as the 

 sun is south of tho equator, or has south declination, he must be 

 invisible from the pole ; but that, as soon as his upper limb touches 

 the equator, ho will begin to rise. In these latitudes sunrise and 

 sunset are phenomena referable to the axial rotation of tho earth, 

 but this quite evidently cannot he the case at the Pole, where, as 1 

 have said above, tho diurnal circle of a star is parallel to tho horizon. 

 The sun, then, at the North Pole will only rise at the same 



rate as ho increases in north declination. Lot us take March 21, 

 when he has Ix-on invisible there for six months. We find from ihc 

 SautinU Atnuinar, that between tho 20th and 2lHt the sun is 

 moving northward at a mean rale of 5023° jxirhour. At this date his 

 diameter is 32' 10 1", or 1030 1". If, then, wo divide 1030 1" by 

 .V.f23", wo shall obtain 32'5SC5, the number of hours the sun will 

 occupy in rising. During 2-t out of these 32'58C5 hours, tho earth 

 will iiavo turned once on her axis, so that the rising sun will have 

 travelknl through 300° [more nearly 361°. — Ei>.] of the horizon. 

 There ore, however, yet 85HG.5 hours to elapse ere he will bo wholly 

 above the horizon ; and during this perifxl the arc ho describes may 

 be approximately found by the ,'proportion 2-t : 8'58(i5::3G0° : the 

 arc re()uired [with a slight correction for refraction. — En. J. 



I should think that "X. X." (query 214) woald find Mayer ami 

 Barnard's little book on " Light," and Mayer on " Sound," both in 

 tho Wo (u re series, the very things for him. Tomlinson'a "Pneu- 

 matics," in Woale's series, will furnish him with numorous in- 

 teresting facts about the atmosphere ; and Tyndall's " Lessons in 

 Electricity," published by Longmans, will supply him with all he 

 needs for a lecture or lectures on the subject on which it treats. 

 A Fellow of the Koval AsrEoNouicAL SociEn'. 



FLEXURE IN PLANES. 



[28C] — There has been a bad epidemic of flexure among planes 

 lately. From all directions I have heard that their sufferings have 

 been severe ; I have also suffered with them. W^ill you allow mo 

 to state through your columns, without encroaching unduly upon 

 your valuable space, that in every case I have traced the flexure to 

 ill-treatment on tho part of the possessors of tho i)lane8. They 

 ha\'e been subjected to torture ; they have been firmly wedged into 

 cells too small for them ; they have had pieces of card jammed in 

 behind them ; they have had screws and clips binding them ; but, 

 above and beyond all, they have been cemented on to wooden 

 blocks and metal plates with h.ard cement, the cooling or setting of 

 which has entirely altered their figure. 1 wish, then, to take 

 advantage of your kindness to inform all those who are interested 

 in the subject, that planes will not give accurate definition under 

 high powers if they arc subject to • restraint in any way. A glass 

 plane 4-in. thick, if attached to a block by a wafer, which is allowed 

 to get hard, will show, as a result, flexure, and give a bad definition. 



John Bbow.m.ng. 



INTERIOR HEAT OF THE EARTH. 



[287] — This ia a subject in which I have always taken a deep 

 interest, and have followed attentively all that has been published 

 in connection vrith it for many years. I have, therefore, been 

 much surprised at meeting with no alltision in any of our English 

 scientific works or periodicals to a book ])ublished in Germany so 

 long ago as 1875 (I give the title of the book below), and which, I 

 understand, met with considerable support from geologists in that 

 country.* 



The author (since dead) was Professor of Chemistry and Physios 

 at Bonn, and professes to found his theories on chemical and 

 physical principles, as ascertained by the latest researches. 



He entirely rejects Laplace's " Nebular Theory of tho Formation 

 of the Earth," denies on chemical and physical grounds its interior 

 heat, and adduces, among other proofs, the results of a great boring 

 undertaken by the Prussian G^ivenimont in 1S70-71, at a place near 

 Berlin, which was carried to a depth of 4,517 ft., mostly through a 

 continuous stratum of rock salt. The heat at first increased at the 

 rate of 1° for 60 ft., but after reaching the depth of 2,000 ft., this 

 increment gradually diminished, so that instead of being IW at 

 the bottom of the boring, it was only 113°. 



He has a now theory to account for earthquakes and volcanoes, 

 the former, ho thinks, being principally caused by the hollowing 

 out of cavities on tho superficial strata by the action of water, and 

 the consequent collapse of these cavities. 



He denies the igneous origin of what are called eruptive rocks, 

 and, among other proofs, adduces the fact of his having found, on 

 an analysis of a very hard piece of granite, some of the nodules of 

 hornblende, surroimded by pure asjihalt. nnchiuiged, which, he 

 observes, would not have remained there if the rock had been 

 subjected to the action of groat heat. 



The coal measures, he maintains, were formed entirely by marine 

 plants, of wliich, he says, there were (and now are) immense forests 

 in tho sea. 



These and many other theories, entirely opposed to the opinions 

 usually hold by geologists in general, he maintains with con- 



• Geschichte der Erde ; ein Lelirbuch der Goologie auf nener 

 Grundlage. Von Friedrich Mohr, Professor zu Bonn. Verlag von 

 Cohen und Sohn, Bonn, 1875. 



