Jan. 28, 1875: 



NA TURE 



259 



rtmaikable result relating to the particular case where the 

 .'.ttracted point P is in the focal hyperbola of the ellipse, viz. : 

 if we consider the semi-axis minor as constant, but the semi-axis 

 major (and therefore also the focal hyperbola) as variable ; and 

 take the point P, always in the focal hyperbola, at a constant 

 altitude above the plane of the ellipse ; then the potential re- 

 mains constant. The potential of the circle is of couise included 

 in the general formula for the ellipse, but there are some special 



invcsligations which .are developed In detail in the paper. — Mr. 

 tilaishev then proceeded to give a sketch of a second paper by 

 I'lof Cayley, on the attraction of an ellipsoidal shell. The 

 i-hell in question is the irdefmitely thin shell of uniform density 

 included between two similar and similarly situated ellipsoidal 

 surfaces. It was known for a long time that the attraction of 

 such a shell on an internal point was equal to zero ; and in 1833 

 Poisson showed analytically that the attraction on an external 

 point was in the direction of the normal to the confocal ellipsoid 

 through the attracted point, or (what is the same thing) in the 

 direction of the axis of the circumscribed cone having the at- 

 tracted point for its vertex. In 1834 Steiner gave a very elegant 

 geometrical demonstration of Poisson's theorem, but did not at- 

 tempt to complete the solution so as to obtain the attraction of the 

 shell. This was done two years ago by Prof. J. C. Adams, F. R. S., 

 who gave the solution at a lecture given in Cambridge. The result 

 (which in the present paper is worked out in a different way) 

 comes out with great simplicity, and we obtain, tvil/ioiit atiy 

 process of integration, for the attraction of the shell a finite ex- 

 pression which coincides with known formulae, and which leads 

 very easily to the known formulae for the attraction of a solid 

 ellipsoid. — Mr. J. Hammond read a paper on the solution of 

 linear differential equations in series. He first takes the general 

 equation and expands y in a series of determinants, the it arbitrary 

 constants being the first n differential coefficients of y when x is 

 ]jut equal to zero, the particular integral being also expanded in a 

 teries of determinants. He then gives expansions of the same form 



fur "!— — and and a value of the ?«th differential coefficient of 



'J'(-v) (f-i-r) 



"' "'' in the form of a determinant of m -I- I rows. And lastly, 

 "^-t-i-) 



he considers tw o particular cases of the expansion of y in series 

 from its differential equation. — Major J- R- Campbell exhibited 

 two " Mechanical Calculators." The instrument is little more 

 than a development of the circular slide scale in which two prin- 

 ciples are engaged in one arrangement : (l) that of the common 

 .■•lide scale ; (2) that of the scale invented by the late Dr. 

 Roget (see article " Slide Scale," by De Morgan, in the ".Penny 

 Cyclopa'dia. ) The designer described the construction and ap- 

 plication of the instrument, and having been thanked by the 

 chairman for his communication, piesented both instruments 

 (which were constructed with extreme neatness of penmanship) 

 to the Society. Major Campbell also presented his description 

 of the instrument to the Society, containing notes on its manu- 

 facture, tables of logarithms, and log-logarithms employed in the 

 construction. — Mr. J. J. Sylvester, F.R.S., made a brief com- 

 munication on the representation of any unicursal curve and its 

 nodes in terms of the parametric coefficients, and on Roberts' 

 and Hart's cases of unicursal 3-bar motion. M. Camille Jordan 

 spoke on the subject of Mr. Sylvester's communication 



Zoological Society, Jan. 19. — Mr. Robert Hudson, F.R.S., 

 vice-president, in the chair. — The Secretary called attention to 

 a letter received from a correspondent in Temate, Moluccas, irr 

 which it was stated that the writer had living examples of four 

 species of Paradise Birds in his possession, namely, of Paradisea 

 papuana, Sdcitcidcs alba, Diphyllodes speciosa, and Ptilorhis 



viagnifica. — A communication was read from Mr. J. Brazier, of 

 Sydney, N.S.W., giving descriptions of ten new species of 

 Australian shells, from the collection of Mr. A. Coxen, of Bris- 

 bane, Queensland. — Mr. A. G. Butler read descriptions of four 

 new species of butterflies of the genus Prologoniiis, belonging to 

 the collection of Mr. H. Dnice. — A communication ^was read 

 from Messrs. P. L. Sclater and O. Salvin, giving descriptions of 

 three new species of South American birds. These were proposed 

 to be called jMicroccrcubcs sqiianndatus, Automolus striaticcps, 

 and Tigrisoma siliiioiii. — Prol. Newton, F. R.S., gave an account 

 of a MS., in the French Archives de la Marine, which con- 

 tained some additional evidence as to the original fauna o 

 Rodriguez, and called special attention to the unknown writer's 

 account of the terrestrial birds of that island, amon;;st which 

 were mentioned the " Solitaire," the Erythromachus Icguati o 

 A. Milne Edwards, and other now extinct forms. — A commu 

 nication was read from Dr. A. B. Meyer, director of the Roya 

 Natural History Museum, Dresden, containing the descriptioir 

 of a new Bird of Paradise, skins of which had been sent to him 

 by Mr. van Musschenbroek, the Dutch Residerrt at Temate, and 

 which it was proposed to call Diphyllodes Giilicbui III. The 

 habitat of this new bird is stated to be the irrner mountains of 

 Eastern Waigiou. — A comrrrunication was read from Major 

 II. H. Godwin- Austen, containing supplementary notes on a 

 forrrrer paper on the species of Hdicida, of the sub-genus 

 Phetopylis. 



Meteorological Society, Jan. 20. — Dr. R.J. Mann, pre- 

 sident, in the chair. — After the Report of the Council had beeti 

 read by the Secretary and adopted, the President delivered his 

 address, in which he dwelt in detail »pon the various important 

 and useful nreasures that had been carried out by the Society 

 during the past year, and in doing so alluded to the action of the 

 Maritime Conference in forwarding uniform and consentaneous 

 operations on the part of meteorologists ; the establishment of a 

 uniform system of record, by the combined action of the Society 

 and the Meteorological Office of the Government, which has 

 been adopted by the Army Medical Department ; and the start- 

 ing of a considerable series of authorised and carefully inspected 

 observatories, which have been planned upon a geographical 

 b.ise, so as to give a comprehensive grasp of the meteorology of 

 lingland, and so as to enable returns to be periodically made 

 which will present at a glance the leading features of climate and 

 season. The value of these stations, it was pointed out, had 

 beeir very materially increased by a system of concerted action 

 which had been agreed upon between the Meteorological Society 

 and the Meteorological CJffice of the Government, and which it 

 was intended to extend as the best and most available situations 

 for other observatories could be determined upon. The President 

 next spoke of the large addition that had been made to the use- 

 fulness of the Society by the acquisition to its ranks of a con- 

 siderable number of the most distinguished meteorologists of 

 foreign lands; of the importance of a scientific alliance with the 

 Public Officers of Health, who are now so closely connected 

 with meteorological investigations ; of the influence of exceptional 

 seasons upon the health of the community ; of investigations in 

 progress with the climate, and especially the winter climate, of 

 London, nov/ of daily importance to some three millions and a 

 half ; of systematic observations of the influence of seasons upon 

 animals and plants ; of the formation by the Society of a library 

 of standard meteorological works ; and of the introduction of close 

 study of the physical condition and aspects of the sun in connec- 

 tion with changes of weather and vicissitudes of season, a subject 

 which is now getting to be of surpassing interest on account of 

 the brilliant discoveries and marvellous deductions that have 

 recently been made in this noble branch of scientific research. 

 The following gentlemen were elected Officers and Council for 

 the ensuing year : — President, Robert James Mann, M.D., 

 F.R.A.S. Vice-Presidents: Charles Brooke, M.A., F.R.S., 

 F.R.C.S., Henry Storks Eaton, M.A., Rogers Field, B.A., 

 Assoc. Inst. C.E., Capt. Henry Toynbee, F.R.A.S. Treasurer, 

 Henry Perigal, F.R.A.S. Trustees : Sir Antonio Brady, F.G.S., 

 Stephen Wrlliam Silver, F.R.G.S. Secretaries : George James 

 Symons, John W. Tripe, M.D. Foreign Secretary, Robert H. 

 Scott, M.A., F.R.S. Council : Percy Bicknell, Charles O. F. 

 Cator, M.A., Cornelius Benjamin Fox, M.D., Frederic Gaster, 

 William John Harris, M.R.C.S., James Park Harrison, M.A., 

 John Knox Laughton, M.A., F.R.A.S., Robert J. Lecky 

 F.R.A.S., William Carpenter Nash, Rev. Stephen J. Perry, 

 M.A., F.R.S., WilUam Sowerby, E. O. WUdman Whttehouse, 

 F.R,A.S., Assoc. Inst. C.E. 



