ii6 



NA TURE 



[Dcr. 2, 1886 



some future endeavour, should the country concerned seem to 

 desire it. The scheme suggested was laid before the members 

 of the present Council, but there was not an adequate oppor- 

 tunity of discussing it, and it will of course come before the new 

 Council. Should they approve of some such measures as those 

 recommended by the Committee, they will doubtless assure 

 themselves in some way or other that those measures are in 

 accordance with the wishes of the Fellows at large before they 

 are incorporated into the Statutes. 



But in connection with this subject there is another suggestion 

 which I would venture to offer, and which I know has been 

 thought of by others. 



A good many years ago it was not unusual to elect to the 

 Fellowship men of distinguished eminence in departments other 

 than scientific. More recently a change was made in the Statutes 

 where y Privy Councillors are enabled to become Fellows by a 

 special method, without interfering with the selection by the 

 Council of fifteen from among the candidates whom they recom- 

 mend to the Society for election. This to a certain e.xtent super- 

 seded the nece^sity of appealing to other than scientific cl.aims, 

 .and in some respects the method had special advantages. Those 

 who attained to a place on Her Majesty's Privy Council were 

 sure to be distinguished men, whom we should be glad to wel- 

 come among us ; and by confining the privilege of special 

 election to these, with whose appointment the Council had 

 nothiuL; to do, all invidious distinctions were prevented. But 

 the method has the disadvantage that it applies only to a parti- 

 cular class of merit. A man, for instance, might be of quite 

 first-rate eminence in poetry or literature, but that would not 

 lead to a seat on the Privy Council. Such a man could only be 

 elected by being placed on the selected list of fifteen. But it 

 seems to me that there is .something not quite courteous either to 

 the eminent man himself, or to the scientific man who would 

 have to be passed over to make room for him, in thus putting 

 him in competition with those who seek admission on purely 

 scientific grounds. I cannot help thinking that it might be well 

 if the Council had the power of recommending for special 

 election men of high distinction on other than scientific grounds, 

 whose connection with us would on both sides be felt to be au 

 honour, and who, though not, it may be, themselves scientific, 

 might usefully assist us by their counsel. I do not think it would 

 be difficult to devise means for providing that such a privilege 

 should be accorded only in case of very high eminence. 



The application of photography to the delineation of celestial 

 objects has of late years made rapid strides ; and, partly owing 

 to the improved sensitiveness of the plates, partly to greater 

 exactness in regulating the motions of equatorially-mounted 

 telescopes, it has been found po~sibIe to photograph even minute 

 stars. The question is accordingly now seriously entertained 

 whether we may not trust to photography for the formation of 

 star maps and star catalogues, taking eye-observations on a suffi- 

 cient number of stars here and there for reference, and trusting 

 to differential measurements taken on the plates for determining 

 the positions of the other stars. Indeed, I think the practica- 

 bility of this application may now be considered as established, 

 and there only remains the question of the best mode of carrying 

 it out on a uniform plan. In the course of the autumn I had a 

 letter from Admiral Mouchez, Director of the Paris Observatory, 

 in which he informed me that in response to the presentation of 

 specimens of the admirable star photographs taken by the MM. 

 Henry, several of the astronomers to whom they had been sent 

 suggested that it would be well that a conference of astronomers 

 of various nations should be held, with a view to taking con- 

 certed .action for obtaining on a unif )rm plan a complete map of 

 the whole starry heavens. He wished accordingly to obtain an 

 expression of opinion on the part of the Royal Society as to the 

 desirableness of holding such a conference ; and as it was contem- 

 plated, in case the proposal should be favourably entertained by 

 those consulted, that the conference should be held at Paris in 

 the spring, and it would be necessary to give timely notice to the 

 astronomers who live in the southern hemisphere, an early reply 

 was requested. 



As it would have defeated Admiral Mouchez's object to wait 

 till the Council should re-assemble after the recess, I wrote at 

 once to consult four of our Fellows specially named by Admir.al 

 Mouchez ; and on receiving their replies I wrote to Admiral 

 Mouchez, saying that under the circumstances I took it upon me 

 to express in the name of the Uoyal Society our approval of the 

 suggestion, explaining at the same time that I did so on the 

 understanding, which I fully be'ieved to be in accordance with his 



intention, that the astronomers who might attend the conference 

 should not be considered as pledged to the adoption of the 

 methods or scale of the MM. Henry, but that the whole subject 

 should be open to discussion. On reporting what I had done to 

 the Council when they met after the recess, I obtained an expres- 

 sion of their approval. 



In these photographs a remarkable instance was exhibited of 

 the power of photography to reveal the existence of objects 

 wholly invisible to the eye. One of the stars of the Plei.ades 

 was found to be surrounded by a nebula which cannot be seen 

 with telescopes. The reason of the difference of power of the 

 plate and eye is very obvious : with the eye an object is either 

 seen or not seen at once, whereas with the plate, provided there 

 be an absence of stray light, feebleness of intensity can be made 

 up for by length of exposure. 



But the MM. Henry are by no means the only persons who 

 have applied photography to the delineation of the stars. Among 

 others, our Fellow, Dr. Gill, who has sent us some excellent 

 specimens of the photographs obtained by his instrument, pro- 

 poses to take at the Cape Observatory photo;^raphs of the whole 

 starry heavens of the southern hemisphere, under such conditions 

 as to include the magnitudes contained in Argelander's " Duich- 

 musterung " of the northern hemisphere, and to subsequently 

 reduce the observations so as to complete Argelander's great 

 work by extending it to the southern hemisphere. Prof. Kapteyn, 

 in Holland, has nobly undertaken to devote his spare time for 

 seven years to superintending the reduction. Dr. Gill has laid 

 the proposal before the Government Grant Committee. Having 

 regard to the magnitude of the undertaking, and the probability 

 of a conference of astronomers being shortly held in Paris to 

 discuss the whole question, the Government Grant Commiitee 

 suggested to the Council of the Royal Society that they should 

 appoint a committee to take the subject into consideration, and 

 the Council have acted on this suggestion. Dr. Gill intends to 

 come to Europe in the spring, so that the committee will be able 

 to consult him personally. 



This morning I received through the Foreign Office an invita- 

 tion from the Academie des Sciencci for myself and some other 

 delegate of the Royal Society to attend the conference to which 

 I have already referred, which is fixed for April 16. I shall 

 take the first opportunity of consulting the new Council as to 

 their wishes. 



The Copley Medal for this year has been awarded to the 

 veteran in science, our Foreign Member, Prof. Franz Ernst 

 Neumann, for his researches in theoretical optics and electro- 

 dynamics. 



Havm^ in his earlier years treated of crystallographic subjects 

 almost half a century ago, he turned his attention to the theory 

 of light. Fresnel had, with his wonderful sagacity, arrived at 

 his celebrated laws of double refraction from ihe theory of trans- 

 verse vibrations, aided by conceptions derived from a dynamical 

 theory which was only in part rigorous. Cauchy and Neumann, 

 independently of each other, were the first to deduce from a 

 rigorous dynamical calculation, applied to a particular hypothesis 

 as to the constitution of the ether, laws of double refraction, not 

 indeed absolutely identical with those of Fresnel, but closely 

 I'esembling them. In this case the laws were known beforehand. 

 But in a very elaborate later paper. Prof. Neumann deduced 

 from theory the laws of crystalline reflection, laws which appear 

 to agree with the observations of Seebeck, and which had not 

 been discovered by Fresnel, though some of them were indepen- 

 dently and aliout simultaneously obtained by MacCuUagh. 



Prof. Neumann is perhaps still better known in connection with 

 the theory of electro-dynamics, and the mathematical deduction 

 of the laws of induced currents due to the motion of the primary 

 and secondary conductor. He may be said to have completed 

 for the induction of currents the mathematical treatment which 

 Ampere had applied to their mechanical action. 



Of the two Royal Medals, it is the usual, though not invari- 

 able, practice to award one for the mathematical and physical, 

 and the other for the biological sciences. 



One of these medals has this year been awarded to Prof. 

 Peter Guthrie Tait, for his various mathematical and physical 

 researches. 



Prof. Tait is well known for his numerous and important 

 papers in both pui-e mathemathics and physics. The late .Sir 

 Wdliam Hamilton regarded him as his own successor in carrying 

 on and completing the newly-invented calculus of quaternions, 

 of which Prof. Tait is continually making new .applications. 

 Among his investigations in the domain of experimental physics 



