396 



♦ KNOWLEDGE ♦ 



[June 29, 1883. 



aa to what mnst be tho condition of the outer surface 

 of tho gascoua envelope of tho sun. Obviously gas 

 is there, |)as.>iinf{ from tho condition of tho third to tho 

 fourth state of matter, and tho mean velocity of tho molecules is by 



Jonlo's equation V = -v/ 3- where V = mean velocity, p=pre88uro, 



^ . P 



p — density. These terms wo cannot determine, bnt may form an 

 idea of the state of affairs since V for hydrogen molecules at 

 32" F., and 30 in. barometer pressure is C,097 ft. per second, and 

 thus individual molecules may be moving at a far higher velocity. 

 Is it not thence almost a nocciiiKinj conseijucnce to suppose that 

 molecules mnst be constantly starting off normally to the sun's 

 surface with a velocity that must take them beyond the limits of 

 the sun's gravitation attraction. Hence, further, such molecules 

 will bombard oh/;/ on the side turned toimrds the sun any particles 

 exposed, and this bombardment will act as ic repulsive force vary- 

 ing with the surface as theory requires. Freb. F. Grensted. 



DO SPECIES CHANGE? 



[862] — I should feel much obliged to you if you could find room 

 for the following extract from Tit-Bits, and should be glad if some 

 one would reply totliesame: — 



" The negroes who attended Semiramis and Rhamses are in every 

 respect similar to the negroes now toiling amid the sugar canes of 

 Alabama. If duriug 4,00U years species and races have not changed, 

 why should we suppose that they ever should change ? ^Vby 

 should we not take our stand on that testimony, and assert that 

 species are unchangeable ? Such has been the argument of 

 Cuvier and his followers, an argument on which they have laid 

 great stress, and which they liave further strengthened by a 

 challenge to adversaries to produce a single case where a transmu- 

 tation of species has taken place. 



" Here we show you evidence that species have persisted un- 

 altered during 4,000 years, and you cannot show us a single case of 

 species having changed ; you cannot show us one case of a wolf 

 becoming a dog, an ass becoming a horse, a hare becoming a rabbit. 

 You must admit that if there were any inherent tendency to change, 

 4,000 j-ears is a long enough period for that tendency to display 

 itself in ; and we ought to see a very marked difference between 

 the species which lived under Semiramis and those which are living 

 under Victoria. Jnstead of this, we see that there has been no 

 change : the dog has remained a dog, the horse has remained a 

 horse ; every species retains its well-marked character." 



R. P. B. 



["E. P. B." will find that the considerations here touched upon 

 have been carefully weighed by evolutionists, and form part of the 

 evidence on which the modern theories of biological evolution are 

 based. They may have been advanced, perhaps, in the present 

 case by some naughty person anxious to show that, if negroes 

 have remained unchanged for 4,000 years, the different branches 

 of the human family can hardly have sprung from a single race, still 

 less from a single pair, unless many millions of years have elapsed 

 since the race began. — E. P.] 



OKIGIX OP THE WEEK. 



[863] — I have been much interested in " The Great Pyramid," 

 and I think, perhaps, the following quotation in reference to " The 

 Origin of the Week " may be of use : — 



" Q. Curti Rufi liistoriarum Alexandri magui Macedonis." — Lib. 

 viii., ab initio cap. is. Cambridge : Pitt Press. 



Book viii., ch. ix., sec. 35 : — 



" Menses in qninos denos discripseruut dies, anni plena spatia 

 servantur. Lunce cnrsu notant tempera, non, nt plerique, cumorbem 

 sidus inplevit, sed cum so curvarc coepit in cornua, et idcirco 

 brcviorcs habent menses, qui spatium eorum ad hunc lunae modum 

 dirigunt — multa et alia traduntur, quibus morari ordinem rerum 

 haud same opeiTC videbatur." 



Trans. — " They (the Indians) have divided their year into 

 months of fifteen days each (lit. they have divided their months 

 into fifteen days apiece) , the full period (plural) of the year is 

 (correctly) kept." 



" They measure time (pi.) by the course of the moon — not, as is 

 generally done, from full moon (lit. when the star* has filled its 

 orb), but (from the time) when it has begun to bend its horns; 

 and, therefore, the months of those who fix the duration of the 

 month according to this phase of the moon are shorter. Many 

 other customs, also, are handed down, with which it really does not 

 seem worth while to delay my narrative." 



• " Sidus = constellation = or fnoon sidus lunrc." — Piin. 2, 9,6, 

 Sec. 41. 



1 have copied the translation from one published by J. Hall A- 

 Son, Cambridge, translated by H. J. C. Knight. 



F. Letebton Harris. 



P-S. — Tlio following translation may also be interesting. — Book 

 viii., 9, 31 :— 



" There is one wild and uncouth class which they call ' wise men.' 

 It is with them a noble deed to anticipate the day of doom " 



" 33. Those who live in towns under rules of civilisation are said 

 to bo skilful astronomers (to examine skilfully the motions of the 

 constellations), and to foretell the future— nor do they believe that 

 one thereby hastens the day of death, since — he-can-look-forward-to 

 it without fear " 



LETTERS RECEIVED AND SHOET ANSWERS. 



Jas. Stephensox. It is very difficult to advise in such matters. 

 1 should have thought GuiUemin's " The Heavens" more generally 

 useful than Newcomb's book, admirable though it is. Would not 

 Huxley's " Physiography " suit. By the way, " physiography " is an 

 atrocious word, not in the slightest degree indicating what was in- 

 tended, and almost as discreditable to science as " chromosphere." 

 — Nemo. GuUlemin's " Heavens." As to telescopes, unable to 

 advise. — A. C. P. suggests that my notes (only they are not mine) 

 on " The Face of the Sky " should date from two days after the 

 day of ])ublication, as some readers are reached later than the day 

 for which the notes begin.— A. D. C, C.axtae. Thanks.— S. P. G. 

 I use Boole's Dif. Equations. Other question too vague. — A. E. W. 

 Inconsistent with curved tails. — Hally.^eds. That correspondent 

 was answering some one who had attacked him. Do not want 

 discussion on the point raised. Letters are not articles. One 

 such subject started would send in on us an intolerable load 

 of correspondence. After all, what does it matter? — G. C. Lyox. 

 Have read the cutting. Should say it was a joke ; but if the 

 person named really wrote that, I should imagine mania was 

 about. — Sam. Ki.xes. Xo, I thank you. I think I could very easily 

 show that, with such latitude as you allow yourself, the chances are 

 about a billion to one against your failing to find close corre- 

 spondence. If " Let the earth bring forth grass" (or, lit., "Let 

 the earth sprout forth sprontage") can be interpreted "Let algae, 

 lichens, and fungi appear," then — well, then, anything, so to speak, 

 might (as it were) be interpreted after a fashion anyhow. In my first 

 book I tried something that way myself, but I know better now. 

 As well try riding across country in swaddling-bands. — J. V. E. 

 Thanks. 'The other article has been really deferred preposterously. 

 It shall appear very soon. The other series I should much like to 

 see. I would arrange for its speedy appearance, taking alternate 

 weeks; for, as you say, it would be necessary not to have long 

 delay. — Arasthom. Surely the discount dodge has been sufficiently 

 explained. — Ja.s. A. U. M. Many thanks. See reply in " Gossip." 

 The proofs full of interesting matter. — A. Good. Can no longer 

 forward or insert questions addressed to contributors. — I-N'mciEER. 

 Gravity at any point within the earth is unaffected by the attraction 

 of all matter lying outside a spheroidal sui'face through the point, 

 similar and concentric with the spheroidal surface of the earth herself. 

 — J. A. EoEsox. ilr. Moore simply takes b so as to make one of the 

 multipliers a multiple of 10. — j As.S. The moth which was flying 

 all the time in the railway carriage covered whatever distance his 

 journeyings within the carriage amounted to, not, in addition, the 

 twenty-five miles traversed by the train. So soon as the train 

 started the carriage-full of air was carried along, with the moth in 

 it. — A. R. EoTCORP (in whom I seem to recognise an inverted name- 

 sake) wishes to hear of a remedy for hay fever. — J. M. Rohger. 

 I daresay your 13-fold trisection will do all you claim for 

 it, and that if I suppose, multiply, subtract, divide, Sec, as 

 vou tell me to, the result will be what you say. Bnt 

 suppose I don't?— E. F. Woottox. Thanks.— E. T. P. Can 

 hardly do that. — M. H. Close. Yes ; some mistakes. — Alg. 

 Bray. There are sixteen roots of the equation besides unity. 

 You have evidently still to study an interesting chapter of the 

 theory of equations. — A, H. HtTTH. Thanks. Will use your letter 

 if can possibly find space. — J. W. Dawsox. Know nothing of the 

 plans for that periodical, except that they in no way affect ours. — 

 A. J. Saxtox. Do not know any of their names, nor quite what is 

 meant by an " astronomer-royal to the king of Bavaria." Is it some 

 specially roy.al kind of astronomy they study? — G. W. B. Thanks; 

 will consider when time comes, and space can be found. — -A 

 Learner. We do not work sums. — C. JoHX^iox gives, as a paradox, 

 this — " For every person boi*n, one, viz., himself, dies ; how then can 

 the population increase ? " By way of illustration, eai-ly marriage 

 and large families may be suggested. — W. Ql'ixtin desires to learn 

 how best to chloroform a frog without injuring it. — T. J. Dewar. 

 Thanks. Heat seems to result from other causes than science 

 recognises. 



