82 



NATURE 



[Nov. 29, 1877 



The exception mentioned above is an extract from Clerk 

 Moxwell, which is certainly erroneous, and from which Mr. 

 O'Toole gets a good deal of fun. We will not suggest that the 

 addition of a single word would make the passage correct, for 

 we should be told^ that text-books ought to be perfect. _ But it is 

 only just to mention that the error occurs in an explanation of the 

 name ; in the definition of the thing the error does not occur ; 

 nay, it is expressly contradicted. 



After this is it not unkind to condemn tho?e doctors who drop 

 the name " potential E." and replace it with such phrases as 

 •' E. of repose," &c., implying that the energy in question is not 

 due to motion? By-the-by where is the bull in "passive 

 energy"? and what is the "action" that may be confounded 

 with kinetic energy ? 



B.- 



-Potential E, as meaning " Energy related to Potential 

 Funetions." 



The word Potential may be used in a second sense. This of 

 itself is a trouble to INIr. O'Toole ; but— remembering that your 

 readers may not sympathise with his undisguised antipathy to 

 verbal skylarking — he hastens to add that the two meanings are 

 not only heterogeneous but incompatible. " Surely there is no 

 occasion to stop to prove this." Please do, Mr. O'Toole; we 

 should like to hear you prove something. 



It may be noted that in this opinion and in paragraph 9 he 

 appears to differ from Thomson and Tait. (See their definition 

 of Potential, Nat. Phil., vol. i., § 485). 



C— Potential E. as meaning " Energy of Potency " 

 It appears from a foot-note that " potency " may mean a force. 

 If so, it is strange that the O'Toole— who, throwing off his thin 

 disguise, at the end of Lis letter undertakes the "duty" of a 

 doctor, and tells us that potential E. should be the " energy of 

 a force " — it is strange that Dr, O'Toole should object to the 

 name on this ground. 



But the remarks under this head are chiefly interesting, as 

 indicating the modus operandi of our pseudo-Publius. He does 

 not trouble to examine the definitions of "potential energv." 

 He only looks for explanations of the word " potential." Find- 

 ing scant material in the doctor's utterances, he resorts to his 

 dictionary, hunts up the different meanings of " potential," adds 

 to these their antitheses, and rends his phantoms to pieces. It 

 is scarcely a parody upon his letter to say — we won't trouble 

 about what a civil engineer is, but let us examine the meaning 



of civil. Now civil has" meanings : ( A.) polite, (B.), &c, 



Therefere "civil E." means "polite E.," and "civil E." used 

 as a distinguishing title cannot mean anything else than this, 

 that the other E. is unpolite E. 



As to the whereabouts of Potential Energy. 

 " We shall now pass from the perplexities 'connected with this 

 imlucky name, 'potential E.,' to consider the behaviour of our 

 teachers towards the thing itself." At last Mr. O'Toole will 

 deign to discuss the definitions given by the doctors. Nay, he 

 wanders away into an examination of such rash— but perhaps not 

 inexcusable— phrases as "the potential E. of a raised weight," 

 &c. The proper remedy for the troubles arising on this pomt 

 is "to use words discreetly and comistently." But this is not 

 sufficiently heroic. A local habitation must be found for this 

 "potential E.," although it would seem as vain to inquire into 

 the whereabouts of potential E. as into the whereabouts of Mr. 

 O'Toole's scientific erudition. It is proposed to lodge this E. 

 in the forces, and perhaps it won't do much harm, as we don't 

 know where the forces are. It is proposed, moreover, to sub- 

 stitute "energy of tension " for " potential E," This done, the 

 doctor's millennium will have come. Never mind about altering 

 your conception of this kind of energy ; call it by another name ; 

 give it a weis7iichtwo lodging. There will be no more " confusion 

 about fundamental principles ; " there will be no more slips of 

 the pen or tongue ; theie will be no more puzzled Publii ; and 

 last, but not least, there will be no more O'Tooles to bother the 

 doctors. Well may " verbal skylarking " be despised. What 

 is it beside such gigantic fun as this? 



' And yet I am sceptical. We started by hearing that it was 

 "principally — though not entirely — the doctors who were to 

 blame for this confusion about fundamental principles." Is 

 this proved? Is not another cause indicated in the letter of 

 of "E. G." (vol. xvii. p. 9)? And shall the doctors expect to 

 be rightly understood when Dr. O'Toole's amanuensis admits 

 (vol. xvi. p. 520) that Dr. O'Toole himself has been misappre- 

 hended upon almost every point by one reader at Iea-.t? 

 Cirenctiter, November 13 H". W. Lloyd Tan.ner 



Smell and Hearing in Moths 



In Nature fvol. xvii. p. 72) your correspondent " E. H. K," 

 observes : " 'J. C seems to draw inferences that moths have 

 not the power of smell, but have that of hearing. I feel quite 

 certain they possess the former, but am in doubt about the 

 latter 



" With reference to the sound of the glass, is it not the quick 

 motion of the hand which disturbs the moth ? " 



May I draw the attention of both your correspondents to sonae 

 experiments of mine on this subject which were published in 

 Nature about a year ago ? These experiments, I remember, 

 were quite sufficient to prove to me that moths have the 

 power of hearing shrill notes ; and, until I read the query of 

 " E. H. K." above quoted, I thought that my account of these 

 experiments must have been equally conclusive to any one who 

 read them. On now referring to that account, however, I find 

 that I there omitted to state one of the experiments which was 

 resorted to for the purpose of avoiding the possible objection 

 which " E. II. K." now advances. This experiment was a very 

 simple one, consisting merely in making a sudden shrill whistle 

 with my mouth by drawing the breath inwards, so as not to 

 disturb the air in the neighbourhood of the insect. The latter, 

 however, always responded to this as to other sounds in the way 

 described, although throughout the experiment I took care not 

 to move any part of iny body. 



George J. Romanes 



It was because of my knowledge of facts like those named 

 by " E. H. K." that I was surprised at the apparent inability of 

 moths to smell ammonia. Being no physiologist, I ventured to 

 draw no inferences ; but it occurred to mc to wonder whether 

 the sense of smell differs in kind with d>fferent organisations ; 

 whether, for instance, some substances strongly odorous to us 

 may be quite inodorous to insects, and vice versa. 



As to the experiment on hearing, I do not think it was the 

 movement of the hand which startled the moths. It may con- 

 conceivably have been the vibration of their wings set up by the 

 sound ; but the experiment can easily be repeated with variations 

 by any one interested in the subject. J. C. 



Loughton 



Meteorological Phenomenon 



This morning at about a quarter before ten the sky here pre- 

 sented a most unusual appearance. The air was calm and the 

 sun shining, but not brightly, through a slight veil of cirro- 

 stratus. The sky was mostly covered with fibrous clouds of 

 cirrus or cirro-stratus (I am not quite sure which I ought to call 

 it), the fibres being quite parallel to each other, but in two 

 different strata ; those of one stratum were approximately from 

 north-east to south-west, those of the other from north-west to 

 south-east—so that they seemed to cross each other like the 

 threads of a woven fabric. I think the fibres from north-east to 

 south-west were the highest, but am not quite sure, though it 

 seemed the same to another who was looking on with me. 



Joseph John Murphy 



Old Forge, Dunmurry, Co. Antrim, November 25 



OUR ASTRONOMICAL COLUMN 

 Stellar Systems. — M. Flammarion, in various notes 

 communicated recently to the Paris Academy of Sciences, 

 has been drawing attention to stars which appear to be 

 affected with a common proper motion, or a motion similar 

 in amount and in its direction. Several of his cases, 

 however, are by no means to be styled " Nouveaux 

 systemes Stellaires." Thus the large and uniform proper 

 motions of the southern stars ^' and f^ Reticuli, to which 

 he refers in the Cotnptes Rendns of November 5, were the 

 subject of remark in ;^Nature, vol. xi. p. 328. That 

 there was a probability of a common proper motion in 

 these stars would be evident to any one who inspected the 

 columns in the British Association Catalogue, published 

 in 1845, but as Taylor had not observed them, and the 

 comparison was consequently dependent upon Lacaille 

 and Brisbane only, there was a possibility of mistake. 

 The first confirmation of the large proper motion of the 

 B.A.C. in f ■ was afforded in Jacob's "mean places of 

 1440 stars"— from the Madras observations 1849-53, and 



