594 



KNOWLEDGE 



[May 12, 1882 



force rosultiii); from this motion by 0«; [Why put it vagndy tlins, 

 writing " function of v," when wo know what tlio centrifugal ten- 



dency is, viz., 



R 



?] 



the moment of gravitation towards the sun will then bo reduced to 



-jTj- - )>id^r, nud the latter factor being a positi%'o quantity we have — 



jm, gm, 



R' 



This inequality of attractive moments must determine motion to- 

 ward the snn in favour of . £, and thia condition holding good for 



any value of g and K, it follows that the polar inflow and equatorial 

 outflow must take place, provided only that space is not empty, as 

 supposed by Laplace, but filled with either an elastic or non-elastic 

 fluid. 



To put it in another way, Mr. [Proctor] imagines that, in order to 

 determine an outflow from the snn, it is necossaiy for the centrifugal 



moment m^fv to exceed the moment of gravitation —^, whereas 



according to my view, the value of the former determines only the 

 rate of outflow, but is immaterial as regards the principle of action. 

 The projection of dust is entirely dependent upon the outflowing 

 cnrrcnt. I leave it for Mr. [Proctor] to determine for liimself the 

 velocity of current necessaiy to move a particle of dust of given 

 size and weight away from the sun in opposition to its force of 

 gravity, which I am well aware is twenty-seven times that of the 

 earth on its surface. 



Tlie gaseous current is of course produced at the expense of solar 

 rotation, but this expenditure of energy is relatively much smaller 

 than that lost to our f arth through tidal action, and may be neglected 

 for our present purposes. It is, moreover, counterbalanced by 

 solar shrinkage, as explained in my paper. 



C. Wm. Siemens. 



[I fear Dr. Siemens' way of treating this question is bat too 

 correctly described by himself as patting it in a mathematical garb, 

 for there is only the garb of mathematics, not the thing itself, in 

 the above discussion, and even the garb is not quite correct. For 

 instance, in mathematics the term "moment" is not used as in 

 Dr. Siemens' letter, nor in any way even approaching to his use of 

 the term. One can tell, of course, very clearly what Dr. Siemens 

 means, and therefore, perhaps, it is unimportant whether he cor- 

 rectly expresses his meaning or not — except as showing that dis- 

 cussions of this kind are somewhat outside the usual course of his 

 inquiries and reading (and also, what was, however, already known, 

 that the Editor of Mature has no very profound mathematical 

 knowledge). Turning, then, to Dr. Siemens' meaning, I note that, 

 in the iirst place, proving that a cubic foot opposite the pole and 

 another opjiosite the equator are anequally attracted towards the 

 sun's centre, by no means sufliccs to prove that either will move in 

 any particular way. It would be the tendencies of neighbouring 

 cubic feet we should have to consider, not those of two cubic feet 

 hundreds of thousands of miles apart. Inflow of a mass of 

 vapour opposite either pole would depend on the state of the 

 gaseous matter immediately below it, and it can very readily 

 be shown that the pressures which would exist opposite the 

 polar regions, and the consequent resistance to inflow, would 

 be greater, not less, than at equal distances in equatorial 

 directions. But the chief objection to Dr. Siemens' reason- 

 ing (I was about to call it specious, but it is not so) lies in 

 this, that he considers a certain consequence which would not 

 even follow at all, as though it not only would certainly follow, 

 but haWng followed, would leave things as they were, so far as the 

 circumstances causing inflow and outflow are concerned. Under 

 the impossible conditions he describes, equilibrium would be 

 unstable (though ho does not, as I conceded for the sake of 

 argument last week, pi-ove this), and movements tending 

 to restore equilibrium would accordingly take place ; but Dr. 

 Siemens assumes, in effect, that there will be no tendency towards 

 pquilibrium, but that the forces tending to produce motion will 

 remain all the time unchanged. It is as though having shown that 

 the water forming the hollow of a wave tends to rise, one were to 

 assume that it will rise for ever. 



What Sir John Ilerschel said of the theory that the Zodiacal 

 light is " a solar atmosphere in any proper sense of the word " is 

 true of Dr. Sicmens's supposititious atmosphere, "the existence of 

 such a gaseous envelope jjropngating pressure from part to part 

 subject to mutual friction in its strata, and therefore rotating in 

 the simo or nearly the same time with the central body, and of 

 such dimensions and oUipticity, is utterly incompatible with 

 dynamical laws." The case is certainly not strengthened by 

 reasoning which, while endeavouring to show that the more aggre- 



galod i)arts of the supposed atmosphere have such a figure as is 

 attributed to the outer corona and the zodiacal, assumes never- 

 theless the possibility of equal densities at equal distances opposite 

 the polar and equatorial regions. 



Mairan's views involved rather an c-tccss than a deficiency of 

 centrifugal tendency, and what Laplace did was to show not that a 

 solar atmosphere would extend no further than a certain distance 

 under any conditions, but that no such atmosphere could, beyond a 

 certain distance, share in the solar rotation, without being entirely 

 freed from any tendency sunwards. This does not seem to be 

 what Dr. Siemens supjioscs to have been Laplace's reasoning, 

 seeing that his views would bo rather supported than opposed by 

 such freeing of gaseous matter to travel ontwards. 



Again, there is all the difference in the world between the effect 

 attributed to solar rotation in cHjnstantly expelling gaseous matter 

 thi-oughout an enormous extent of space around the sun, and that 

 tidal action which affects the earth's rotation, not by the actual 

 motion of the ocean, but by the mere transmission of wave states. 



However, the points touched in the two preceding paragraphs are 

 relatively insignificant. — Kicuabd A. Phoctok.] 



CONSUMPTIOX. 



[397] — Anything coming from so brilliant an intelligence as 

 that of Professor Tyndall deserves attention. In this instance, 

 at any rate, he has cut before the point. His conclusions do not 

 justify his premises, his premises his conclusions. They remind 

 one of a statement of his made a few years back, that the air of a 

 sick chamber, by passing through cotton wool, might be made 

 pure as t'ne air of the Upper Alps, forgetful that the carbonic acid 

 of respiration could not be thus eliminated, and the atmosphere in 

 so far rendered pure. Professor Carpenter, going on some state- 

 ments of Professors Villemin and Klebs, informed us that tubercle 

 was owing to a micrococcus or microphyte, a little berry or little plant. 

 Now, we are asked to believe that it depends on a little stick or 

 hacilluSj as Professor Koch terms some presumed organism. 

 These inquirers, however, are led away on a wrong scent. If 

 there be a micrococcus or bacillus met with in tubercle, it 

 is an occurrence entirely loiv^"' y and in no way essential to 

 the production of tubercle itself. I have had as mnch to do 

 with tubercle as most persons, and I never saw any micro- 

 coccus, any bacillus. Tubercle is whoUj' unorganised, in fact, a 

 caput raoriuum, consisting of the unoxidised carbonaceous waste, 

 not excreted by reason of insufficient congress with the oxygen of 

 the atmosphere. Not only tuberculous matter, but almost any 

 extraneous substance is capable, upon inoculation, of producing 

 tubercle in subjects predisposed, so that it is quite unnecessary to 

 torture animals in order to verify this position. The gener.il spread 

 of tubercular disease does not depend upon inoculation, but on the 

 respiration of prebreathed air. If we only avoid prebreathed air, 

 tubercle and tuberculous disease become impossible. At least a 

 fourth of the human race are reputed to perish tubercle-stricken. — 

 I am, sir, your obedient servant, 



Henry MacCorm.\c, M.D., 

 Consulting Physician to the Royal Hospital^ 



[We have inserted Dr. MacCormac's letter, though the Times 

 would not, because in such matters the fullest discussion is desir- 

 able. Albeit there is one point to which I must take exception. 

 Professor Tyndall never made the mistake attributed to him by Dr. 

 MacCormac. I remember jierfectly well his first popular statement 

 of the action of cotton wool in his lecture on dust and disease, and 

 I am sure not a person in the lecture-room supposed for a moment 

 that he meant what Dr. MacCormac implies, viz., that the air was 

 otherwise purified than by the elimination of organic matter. Dr. 

 MacCormac, in his enthusiasm for the theory which ho enunciated 

 in his book on the " Breath Eebreathed," seems able to close 

 his eyes to facts which most students of minute life consider 

 demonstrative. When Dr. Koch not only saw with the microscope 

 (what Dr. MacCormac has not seen) the minute bacilli, but has suc- 

 ceeded in developing and as it were rearing, generation after gene- 

 ration of bacilli, it is rather too much to ask science to reject all 

 belief in these organisms. Nor can wo see how the crucial experi- 

 ments, described so lucidly by Professor Tyndall (Knowledge, 

 p. 51-7), can possibly be controverted by any number o'' experiments 

 showing (what no one doubts) the bad effects of breathing pre- 

 bre.athed air. — Ed.] 



[Several interesting letters on "Consumption" are unavoidably 

 held over.] 



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