SCIENCE. 



237 



appeared very faint. This I attributed to its proximity to 

 the bright star. 



I shall continue the search for it. Tne moon will leave 

 in a few days and I then hope to be able to seethe comet 

 again. E. E. Barnard. 



May 15, 1881. 



CORRESPONDENCE. 



[ The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. No notice is taken 0/ anonymous communi- 

 cations.] 



To the Editor of " SCIENCE :" 



I should have attempted a reply to the restrictions of 

 Mr. Dopp before this time if I had not had my hands too 

 full of other work, but lest any might think I have noth- 

 ing to say if an answer of some kind did not shortly 

 appear, I will ask the favor of a little space, and first I 

 entirely disclaim the pretension of undertaking to recon- 

 struct Physical Science which Mr. Dopp seems to impute 

 to me, and whatever was put forward as new was only 

 hypothetical, and perhaps 1 was not guarded enough in 

 specifying it as such. Yet there is more that may be said 

 for some of the statements made than appears in those 

 papers, which were very brief and did not pretend to give 

 references. But now if I shall deal with the subject of 

 internal and external energy which is attacked in the last 

 part of Mr. Dopp's paper, it will save saying very much 

 about the first part. 



Mr. Dopp quotes from Maxwell's works on Heat, and 

 says they disprove and invalidate all my calculations. 

 But it will probably be allowed to hear Maxwell in 

 1875 against Maxwell of 1872 : 



" In i860 I investigated the ratio of the two parts of 

 the energy on the hypothesis that the molecules are elas- 

 tic bodies of invariable form. I found, to my great sur- 

 prise, that whatever be the shape of the molecules, pro- 

 vided they are not perfectly smooth and spherical, the 

 ratio ot two parts of the energy must be always the same, 

 the two parts being in fact equal." He also says a few 

 lines beyond, when speaking of the researches of Boltz- 

 mann, he " makes the whole energy of motion twice the 

 energy of translation." See Nature, volume 11, p. 375. 

 This language justifies my work and my calculations 

 are not invalidated. What is to be understood by 

 E' — K £, is their difference and not a ratio, and the 

 expression in the paper is wrong, but there is nothing in 

 the paper that depends for its correctness upon any 

 mathematical expression in it, whether it is right or 

 wrong, and cannot be raised against it. That is to say, 

 there is nothing in the first paper that is a deduction from 

 any mathematical work given. 



As to my definition of ether as not matter, again Max- 

 well is quoted against me, and I will therefore again quote 

 Maxwell in my favor. " According to Thomson, though 

 the primitive fluid is the only true matter, yet that which 

 we call matter is not the primitive fluid itself but a 

 mode of motion of that primitive fluid." See v Art. 

 Atom Enc. Brit., 9th Ed. The italics are mine, but if it 

 does not plainly make a distinction between ether 

 and what we call matter, then I don't understand 

 it. But I claim more, that to call ether the primitive 

 matter is to call two different things by the same name, 

 and my first paper was a protest against that. Newton's 

 law of Universal Gravitation states that " every particle 

 of matter in the Universe attracts every other particle of 

 matter," and until it is discovered that ether possesses 

 this property of attraction, I hold that the name matter 

 should not be applied to it. If, however, any one thinks 

 it to be a proper use of words, I shall not quarrel with 

 him, only when he talks to me of matter I shall need to 

 ask whether he means gravitative matter or non-gravi- 

 tating matter. As for the objection that I use the term 

 density applied to ether and am therefore to be held to 

 what is implied in the word ; any one who undertakes to 



express a new conception must either employ words that 

 have some fixed meaning or else coin some new word 

 which in its turn must be defined with old words. So 

 while the term density conveys my meaning in a tolera- 

 ble way, I do not wish to have it imply that density in 

 ether and density in matter are identical. In the same 

 article on Atoms, Maxwell says concerning the vortex-ring 

 theory : " We have to explain the inertia of what is only 

 a mode of motion," and this is in strict accordance with 

 all I have written about it. 



We do know that the motions of atoms set up corres- 

 ponding motions in the ether, and it is not d fficult to 

 perceive how it may happen, though the particular 

 mechanical conditions may not all be known. Assuming 

 that the conditions are mechanical, then the analogy of 

 the vibrating tuning fork is not so far fetched as it might 

 be. I do not see the necessity for my being held to 

 atoms combining in only one plane. It is as easy to 

 see that three or four or more could all unite at the same 

 place so as to form a radial structure or a triangular one 

 when one of the two represented in the diagram should 

 swing round 120 , which, so far as I can see, would not 

 imperil its stability at all, and it then would be in posi- 

 tion for another similar atom to unite with each, and so 

 on almost any kind of a geometrical solid made. But I 

 did not intend to assert at all that in this hypothesis there 

 was anything more than an idea. I am not ignorant of 

 the molecular form of ordinary matter, but my assump- 

 tion was that the molecular form was due to its vibratory 

 energy, and, consequently, I was mostly treating of atoms, 

 and the statement was made that at or near absolute 

 zero the chemical affinity was nil, and hence dissocia- 

 tion. This is plainly the case if chemism is due to heat 

 vibrations, but it is corroborated by mathematical calcu- 

 lations. In a paper read before the American Academy, 

 in February last, by Mr. D. E. N. Hodges, of Harvard 

 College, but which has not yet been published, the same 

 conclusion is deduced from thermo-dynamic considera- 

 tions, namely, that at absolute zero "there can be no 

 cohesion of molecules, and probably the same for atoms ; 

 it is the temperature of dissociation." Mr. Dopp quotes 

 from Professor Tait what he knew about the phenomena 

 of vortex-rings, but since Mr. Dopp's paper was written 

 he has probably heard of some more phenomena of vor- 

 tex-rings. See " Science," April 16th. 



As to the paper on Atoms as forms of Energy the idea 

 is not mine, but Thomson's, and whether or not the 

 method therein shown ot computing atomic weights is 

 mathematical jugglery, as Mr. Dopp calls it, all I 

 have to say is, I did not stake anything upon it. I 

 thought if matter is a form of energy, the fact shouk'. 

 appear in atomic weights, and so I made the calculations 

 and published them, and if anyone thinks they signify 

 nothing, why I will not quarrel with him. After so long 

 a paper finding fault with anything I had written, it was 

 something of a pleasure to read that he thinks my theory 

 can be made " a fair working hypothesis to explain adhe- 

 sion, cohesion, and even crystallization, — surface tension 

 of liquids and capillary attraction, and possibly those of 

 osmosis, dialysis and occlusion." 



This is not an unworthy stock of phenomena to explain, 

 and if what I advanced can not be made to do all I pro- 

 posed to have it do, I might be content if it explained in 

 a fair way any one of the above phenomena. 



A. E. DOLBEAR. 



College Hill, Mass., May ioth, 1881. 



To the Editor of Science : — 



As two of your correspondents, Mr. A. E. Dolbear and 

 Mr. George W. Rachel, have adversely criticized certain 

 points in my article in the April 9 number of " SCIENCE, 

 and as I still consider my position as stable, I must re- 

 quest a limited space to reply to these gentlemen. 



The main difficulty seems to be that I have gone 



