164 



NATURE 



\_'yune 23, 1 88 1 



LETTERS TO THE EDITOR 



\The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manusiripts. 

 No notice is taken of anonymous communications. 



[ The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible othenvise to ensure the appearance ev:n 

 of communications containing interesting and novel facts.'\ 



The Electric Railway in Paris 



I HAVE within the last few days received a letter from a friend 

 in Paris, who writes that he had last week travelled on the 

 electric railway in that city. There is still much, he adds, to be 

 done before it can be brought into general use ; but nevertheless 

 the train moved satisfactorily. There were fifty-four passen,;ers 

 in the carriage, which was propelled by a large Gramme machine 

 and 160 cells of Faure's battery. The experiments are to be 

 recommenced very shortly with a new motor by M. de Meritens, 

 and a Faure's battery. \V. Spottiswoode 



41, Grosvenor Place, S.W., June 16 



Probably New Variable and Red Star 



On May 22 I found, 2° 5i'7 north of o Cygni, a deep i-ed or 

 crimson star, which is not in the Bonn Catalogue. The nearest 

 to it there is + 47° 3167, which in declination con-esponds with 

 a white star that I observed at the same time, but not in R. A. 



Dr. Doberck writes to me as follows : — " Markree Observa- 

 tory, 1881, May 29; observed the new star; brick-red, the 

 nicest I ever saw, 8 7 mag. " ; and " 1881, May 31 : ih. a.m., 

 colour same as before ; 8*4 m." 



Mr. Ward of Belfast, who observed in the early morning of 

 May 31 in strong twilight, describes the star as " deep crimson ; 

 beautiful object ; two or three comites." 



Mr. Gledhill, in Mr. Crossley's observatory, Halifax, found 

 it, on May 30, " strikingly red." 



Dr. Ball, the Astronomer-Royiil for Ireland, observing at 

 Dnnsink, saw it "a superb crimson." 



Prof. Krueger, director of the Kiel Observatory, described it 

 as " aujfallend roth" (remarkably red), on May 30. 



On June 2 it appeared to me unchanged in colour, and increased 

 from 9 mng. to 8'4. — June ^ and 8, colour still the same, and 8'3 

 or S'4 maLjnitude. 



Dr. H. Kreutz, writing from the Bonn Observatory, states 

 that he finds an observation of the star recorded on June 19, 1S57, 

 but not at any other time during the progress of the observations 

 for the Bonn Catalogue, in which it has not been published. 

 There does not appear to be any note of its colour, and I 

 think it will most likely prove a variable of a very remark- 

 able character. Prof. Krueger makes its position for 1855 

 = a 2oh. 36m. 37s. -9 ; 547° 37' 33". Herr Kreutz's position is 

 a 20h. 36m. 37^. "O ; 5 47° 57'"9. The white star mentioned 

 above is not recorded in any of the Bonn observations ; and, on 

 tlie other hand, I may add that I do not identify + 47° 3167 in 

 the telescope. I estimated the w-hite star at about 9'5 mag. of 

 Argelander's scale, and therefore within the limits of the 

 Durchmiisterung. 



The small stars seen by Mr. Ward are perhaps too distant 

 to be strictly considered as comites to the red star. They 

 are sufficiently difficult to me, though probably easy to his well- 

 known extraordinary sight. The position of the nearest that I 

 see is about o", and I find two others more distant — one at 350°, 

 and one at 110°, with a power of 120° on a i\\ inch O.G. 



There seems a peculiar dimness about the star, referable, 

 probably, to the dark shade of its red. An uneducated person 

 with a very excellent eye, and who never heard a description of 

 a red star, compared it, at first view, to " a drop of black blood." 

 It may be conveniently and well compared \\\\\\ Nos. 44S and 

 SS3 of my " Red Star Catalogue," especially with the former, 

 the colour of which was described by Secchi as "intense" ; and 

 in the glowing red of the one object will be remarked a striking 

 contrast with the deep sombre tint of the other. 



I make the approximate positions of the red and the white 

 stars for 1855, and corrected from my first obserrations, as 

 follows: — 



h. m. s. , , 



The red 20 36 27 ; -H 47 37-5 



Thewhite 20 36 l8 ; -I- 47 46-8 



Argeliinder's position of his 4- 47° 3167 20 36 28 ; -f 47 46-8 



Millbrook, Tuam, June 3 John Birmingham 



The Doctrine of the Conservation of Electricity 



I WISH to take the earliest opportunity of responding to the 

 courteous letter of M. Lippmann, which appears in the current 

 issue of Nature, with the acknowledgment that his quotation 

 from the Comptes rendus of 1876 establishes in the most con- 

 clusive manner his priority of date in the enunciation of the 

 doctrine of the Conservation of Electricity. As to my own 

 independent enunciation of this doctrine, it was arrived at with- 

 out any knowledge of the comparison drawn by M. Lippmann 

 in 1S76 between the cyclical flow of heat (of Carnot's theorem) 

 and the cyclical How of electricity. I approached the matter 

 upon somewhat different and less clearly defined lines, and 

 finally struck upon the fundamental notion of the Conservation 

 of Electricity when endeavouring to think out the relations 

 between electromotive and po ideromotive force in an electric 

 theory of radiation based upon Clerk-Maxwell's Electromag- 

 netic Theoiy of Light. My speculations on this point were 

 committed to writing some weeks ago, and will shortly be pub- 

 lished. I content myself in the meantime with pointing out how 

 near Clerk-Maxwell came to a similar conclusion. In Article 35 

 of his well-known treatise, he says emphatically: "While ad- 

 mitting electricity, as we have now done, to the rank of a physical 

 quantity, we must not too hastily assume tliat it is, or is not, a 

 substance, or that it is, or is not, a fonn of energy, or that it 

 belongs to any known category of physical quantities. All that 

 we have hitherto proved is that it cannot be created or anni- 

 hilated" (the italics are mine). Nevertheless the immediate and 

 logical conclusion that electricity, like matter and like energy, is 

 subject to a law of conservation, appears to have been rejected 

 by Clerk-Maxwell for reasons explained in Article 574 of his 

 treatise, con equent on his inability to discover whether an 

 electric current possessed momentum or could exert a mechanical 

 reaction upon the matter of the conductor through which it flows. 

 The unfortunate dilemma w-hich suggested this experiment could 

 hardly have been raised if it had then been as clearly understood 

 as it now is that there is the same distinction between electro- 

 kinetic and ponderokinetic energy as between electromotive 

 and ponderomotive force. But to di-cuss this matter further 

 would lead me to take up too much space. 



Silvanus P. Thompson 

 University College, Bristol, June 19 



Thought-Reading 



It would seem that the "discovery" of reading people's 

 thoughts, lately mentioned in the daily papers^ is in no way essen- 

 tially different from the well-known "game " of " wishing " often 

 played by young ladies. It consists of the following procedure. 

 One person goes out of the room, while others arrange upon what 

 she is to do. She enters blindfolded, and in the particular instance 

 now alluded to, was turned round several times so as to be quite 

 unconscious of the direction in which she was facing. Two 

 persons now place their hands on either side of each shoulder, 

 making their fingers meet at the back of the neck and under the 

 chin ; or they may be placed round the waist ; but as the fore- 

 head appears to be equally sensitive, perhaps it is immaterial 

 where the hands be situated. After standing still a moment or 

 two, the lady moved slowly round in the direction of a sofa 

 under the impression, as she afterwards said, that she was 

 walking in quite another way. Having reached it, she sat down 

 (not even knowing the sofa was close by), and deliberately put 

 ont her hand, took up an antimacassar which lay upon the sofa, 

 and raised if, asking, " Is this what I was to do?" This was 

 perfectly correct, tlie antimacassar having been expressly laid 

 there for the purpose. 



It was settled that another lady should walk into the conserva- 

 tory. To do this she had to pull up a blind, lift an iron bar and 

 open the shutters, then undo the glass door behind them which 

 led into the conservatory. All this she did unhesitatingly, and 

 walked straight into it. I could describe several other instances 

 where ornaments and other things had to be selected out of 

 various groups of objects, &:c. : but the above will illustrate the 

 process. 



One essential condition of success is that the individual must 

 voluntarily and entirely surrender the will, while those who hold 

 the person blindfolded must determine as powerfully as they can 

 that the latter shall do what they wish. Care should be taken 

 not to push the individual in the desired direction. This how- 

 ever may be done involuntarily, but it will not account for the 

 person doing all that has been previously determined after 



