562 



NATURE 



[April 26, 1877 



be the subject of a special report. From the Pelew Islands the 

 indefatigable traveller proceeded to the southern and then to the 

 northern shore of Admiralty Island, noticing the remarkable 

 prognathous development of the Melanesian natives of this 

 island, as well as those of the island Agomes, of the Hermite 

 Archipelago. After a short visit to the Ninigo Islands, Dr. 

 Maclay returned to the shore bearing his name, the natives of 

 which received him very kindly. He built a house for himself, 

 where he intended to remain, pursuing his anthropological 

 researches. 



The Jour7ial of Forestry and Estates Management is the title 

 of a new shilling monthly, which will appear on May, i pub- 

 lished by Messrs. J. and W. Rider, of Bartholomew Close, E.G. 

 It will be devoted to the interests of Arboriculture in its scien- 

 tific, practical, and economic aspects, and will give a large 

 portion of its space to matters appertaining to the general ma- 

 nagement of estates. 



We have received through Mr. Tucker, from Mr, J. M. 

 Wilson, Rugby, two guineas towards the Gauss Memorial 

 Fund, 



The inventor of the new electric seismograph referred to 

 last v/eek is not Father Secchi, but Father Cecchi, of the Scuole 

 pie at Florence. 



The additions to the Zoological Society's Gardens during the 

 past week include a Rusa Deer (Cervus rusa) from Java, pre- 

 sented by Mr. A. A. Frazer, F.Z. S. ; a Bay Bamboo Rat 

 {Khizomys badius) from India, presented by Mr. J. Wood Mason ; 

 a Horned Lizard {Phrynosotna cornutum) from Texas, presented 

 by Mr, T. Clover ; a Brown Monkey {Macacus brunmus) from 

 Assam, deposited; a Demeraran Cock of the Rock {Rufieola 

 crocea) from Demerara, purchased ; two Chinchillas {Chinchilla 

 lanigeta), born in the Gardens. 



SOCIETIES AND ACADEMIES 



London 



Royal Society, March 15. — "On the Tides of the Arctic 

 Seas.— Part VII. Tides of Port Kennedy, in Ballot Strait." 

 (Final Discussion.) By the Rev. Samuel Haughton, M.D. 

 Dublin, D.C.L. Oxon., F.R.S., Fellow of Trinity College, 

 Dublin. 



The tidal observations at Port Kennedy were made hourly for 

 twenty-three days ; and in my former discussion of these tides 

 (Part VI.) I used only the observations made in the neighbour-, 

 hood of H. W. and L. W., obtaining the following results for 

 the tidal coefficients : — 



Diurnal Tide. . 

 S = 23 '4 inches. 



= 20 '9 inches. 



M 



Semidiurnal Tide. 

 S — 7 'o inches. 



M = i7'o inches. 



hn •■= - oh 12™. 



In the present discussion I have employed all the hourly ob- 

 servations made during the twenty-three days, and have obtained 

 the following results : — 



Diurnal Tide. 

 S — 36 '4 inches. 



i, ^ 3h 2^, 



M = 18 '5 inches. 



i,n = - 2h 48'". 



Semidiurnal Tide. 



S = 



M 



5 '9 inches. 

 2h 48'". 

 15*5 inches. 



The present more complete discussion fully confirms the 

 result before obtained by me, respecting the great magnitude of 

 the solar diurnal tide at this station, and also shows a satisfac- 

 tory agreement in the other coeiticients obtained from H. W. 

 and L. W. observations only. 



The method employed in tha present paper is based on 

 Fourier's Theorem, by which the height of tide is expressed as 

 follows : — 



+ Ai cos J + A2 cos 2J- + &c., 

 F = Ao 



+ Bj sin J + B2 cos 2J + &c., 



where 



= height of water, 

 hour-anfjle of sun. 



The coefficients Aq, A^, Aq, Bj, Bg, &c., being found by well- 

 known formulfe, they are again expressed, by Fourier's Theorem, 

 as follows : — 



-H a^ cos u + ^2 cos 2M + &c. 



An = «o 



-H b-^ sin M + ^2 sin 2u, 



where u passes through all its changes in a fortnight, and the 

 coefficients are calculated in a similar manner. 



The known theoretical formulse for the diurnal and semi- 

 diurnal tides, expressed in terms of parallax, declination, lunar 

 and solar, hour-angles, are now converted into functions of the 

 true and mean anomaly, and of the sun's hour-angle, and finally 

 into simple functions of s and it. These expansions are now 

 compared, term by term, with the terms of the tidal expansions 

 found by means of Fourier's Theorem, and the final lunar and 

 solar tidal coefficients calculated out with ease. 



Although the short period of observation at Port Kennedy 

 (23 days) renders this method of discussion not much more 

 valuable than the usual method of H. W. and L. W. observa- 

 tions, I have developed it at length in the hope of applying the 

 method to more complete series of Arctic tides, which I hope 

 shortly to lay before the Royal Society. 



March 22. — "On Friction between Surfaces moving at Low 

 Speeds," by Fleeming Jenkin, F.R.SS. L. and E., Professor of 

 Engineering in the University of Edinburgh, and J. A. Ewing. 



The common belief regarding friction, which is based on tiie 

 researches of Coulomb and Morin, is that between surfaces in 

 motion the friction is independent of the velocity, but that the 

 force required to start the sliding is (in some cases at least) 

 greater than the force required to overcome friction during 

 motion ; in other words, the static coefficient is usually con- 

 sidered to be greater than the kinetic. It occurred to the 

 authors that there might possibly be continuity between the two 

 kinds of friction, instead of an abrupt change at the instant 

 in which motion begins. We should thus expect that when the 

 relative motion of the surfaces is very slow there will be a gra- 

 dual increase of friction as the velocity diminishes. Whether any 

 such increase takes place at very low speed is left an open question 

 by the experiments of Coulomb and Morin, whose methods did 

 not enable definite measurements of the friction to be made when 

 the velocity was exceedingly small. The authors have succeeded 

 in measuring the friction between surfaces moving with as low a 

 velocity as one five-thousandth of a foot per second, and have 

 found that in certain cases there is decided increase in the co- 

 efficient of friction as the velocity diminishes. 



The surfaces examined were steel on steel, steel on brass, steel 

 on agate, steel on beech, and steel on greenheart — in each case 

 under the three conditions, dry, oiled, and wet with water. In 

 the cases steel on beech oiled or wet with water, and steel on 

 greenheart oiled or wet with water, the coefficient of friction 

 increased as the velocity diminished between the two limits 

 given above, the increase amounting to about twenty per cent, 

 of the lower value. It appeared that at the higher limit of 

 velocity there was little further tendency to change in the co- 

 efficient, but it is impossible to say how much additional change 

 might take place between the lower limit of the velocity and the 

 higher. In the case of steel on agate wet with water there was a 

 similar but much less marked increase of friction as the velocity 

 decreased. And in the case of steel on steel oiled there was a 

 slight and somewhat uncertain change of the opposite character, 

 that is, a decrease of the friction as the velocity decreased. 

 This case, however, would require further examination. In all 

 other cases the friction seemed to be perfectly constant and inde- 

 pendent of the velocity. Out of all the sets of circumstances 

 investigated, the only ones in which there was a large difference 

 between the static and kinetic values of the coefficient of friction 

 were those in which a decided increase was observed in the 

 kinetic value on the speed decreased. This result renders it 

 exceedingly probable that there is continuity between the two 

 kinds of friction. 



Linnean Society, April 5. — Prof. AUmann, F.R.S., pre- 

 sident, in the chair. — Capt. Chimmo, R.N., the Rev. J. Con- 

 stable, and Prof. Liversidge, of Sydney, N.S.W., were elected 

 Fellows of the Society. — In acknowledging a donation from the 

 author (Mr. H. J. Elwes), of the first part folio, " Monograph of 

 the Genus Lilium," the , President congratulated the Society on 



