i7/«y 30,1878] 



NATURE 



131 



which will be decisive of the question whether the result 

 of Leverrier, that the motion of the perihelion of Mercury 

 is much greater than that due to the action of the known 

 planets, is really correct." So far as the results of obser- 

 vation have been made known, there is every indication 

 that the theory of Leverrier will receive a striking con- 

 firmation therefrom. The observations of first internal 

 contact in Europe are closely accordant with calculation ; 

 and in a telegram from M. Andrd, in charge of the 

 French expedition, despatched through the liberality of 

 M. Bischoffsheim to Ogden, in the Utah territory, for 

 the observation of the transit, it is stated — " sortie con- 

 firme theorie." 



Adopting Leverrier' s diameters of sun and planet, 

 deduced from his elaborate discussion of the transits of 

 Mercury observed to 1832, and the value of solar paral- 

 lax determined by Professor Newcomb (8" '848), we have 

 the following equations for the reduction of observed 

 times of first external and internal contacts to the centre 

 of the earth : — 



h. m. s. s. s. o . / 



First ext. cont. ...3 13 i-o + 74'S3, p sin / + 80-89, p cos /, cos (L-56 49-3) 

 First int. cont. ...3 16 8-4 + 74*92, p sin / + 81-32, p cos /, cos (L-56 2-4) 



Where / is the geocentric latitude, which may be ob- 

 tained together with p, the radius of earth at the point of 

 observation, from Bessel's Tables in the Berliner astro- 

 nomisches Jahrbuch for 1853, and L is the longitude 

 from Greenwich counted towards the east : the resulting 

 times are for Greenwich. We shall give next week a 

 comparison between observation and calculation. 



Encke's Comet.— The Filrstl Jablo7iowskVschen 

 Cesellschaft oi Leipsic have offered a prize in 1881 for a 

 new investigation on the motion of this body, their former 

 similar offer for 1877 not having met with a response. 

 It is urged that the researches of Dr. von Asten, so far 

 as they are known, have not led to any definite result, and 

 other periodical comets not having shown any indications 

 of a resisting action such as is apparent in the motion of 

 Encke's comet, a further complete and separate investi- 

 gation (z/£»//y/a:>/<^i!^^iV,?«(5^rt'r^^//««^) is much to be de'sired. 

 Accordingly the Society's prize of 700 mark is again 

 offered. It is stipulated that all known perturbing forces 

 are to be taken into account, and the calculation is at least 

 to include the period from 1848 to the last appearance 

 of the comet. A similar work for the earlier portion of 

 the interval elapsed since the first discovery in 1786, is 

 reserved as the subject for a future prize. 



In connection with the anomalous motion of Encke' s 

 comet it may be remarked that Brorsen' s comet of short 

 period appears deserving of much closer computation 

 than it has yet received. After that of Encke's comet its 

 perihelion distance is considerably less than in the case 

 of any of the other comets forming this particular group, 

 as the following statement will show. Biela's and 

 De Vico's comets are omitted : — 



Perihelion Distance of Encke's Comet 0*333 



„ I, Brorsen's 0-595 



M )> Winnecke's 0781 



»> >, D'Arrest's 1*280 



.» » Tempel's (1873, H.) ... 1-339 



,, >. Faye's 1-687 



» .» Tempel's 1867, II.) ... 1-769 



GEOGRAPHICAL NOTES 

 The Anniversary Meeting of the Geographical Society 

 on Monday was not marked by any unusual feature. The 

 address of the president— his retiring one, as it turns 

 out— consisted as usual of a comprehensive review of the 

 geographical work of the past year, an unusually event- 

 ful one in exploration. The Society is as prosperous as 

 ever in members and money. There were on April 30 

 3,334 Fellows on the register, of whom no less than 762 

 are life members On the motion of Sir Henry Rawlin- 

 .5on, the meeting adopted an alteration of the rule regu- 



lating admission to meetings of exceptional interest, with 

 a view to obviate certain difficulties which have arisen in 

 this respect. The Royal Medals, the award of which we 

 have already announced, were presented to Count Miinster, 

 the German ambassador, on behalf of Baron F. von 

 Richthofen, the President of the German Geographical 

 Society, and to Capt. H. Trotter, R.E., personally. The 

 schools' prize medals were also presented to the success- 

 ful competitors whose names we have before recorded. 

 From the new president. Lord Dufferin, we may next year 

 expect an address marked by unusual raciness, eloquence, 

 and intelligence ; Lord Dufferin will probably return to 

 this country in autumn. 



The Committee of the African Exploration Fund of the 

 Royal Geographical Society have at length definitely 

 resolved to despatch a carefully organised expedition to 

 explore the unknown tract of country lying between the 

 caravan road which, as we have before mentioned, is 

 being constructed from Dar-es-Salaam (a few miles 

 south of Zanzibar), to the northern end of Lake Nyassa. 

 Mr. Keith Johnston will, we believe, be in command, and, 

 will be accompanied by another European not yet 

 selected. Should this expedition prove successful, and, 

 what is equally important, sufficient funds be forth- 

 coming, the committee contemplate pushing their explo- 

 rations to the southern end of Lake Tanganyika, a further 

 distance of 190 miles, thus completing approximately two 

 of the routes sketched out in the circular issued last 

 summer. In order to enable the committee to despatch 

 this expedition, which is expected to furnish important 

 and valuable geographical information, the Council of the 

 Geographical Society have just made a further grant of 

 500/. to the fund, and it is hoped that the public and the 

 subscribers will lend it such additional support as will be 

 required to carry out the objects in view. 



At the last meeting of the Geographical Society of 

 Paris M. de Lesseps stated that Col. Gordon had pushed 

 the Egyptian advanced posts up to the equator, and that 

 now any traveller can go from Paris to the equator within 

 sixty days if he has procured a letter of introduction from 

 M. de Lesseps, Abbd Debaize, who, as we have already 

 stated, intends to cross Africa, has availed himself of this 

 privilege and is probably now on the banks of the Albert 

 Nyanza. M. de Lesseps states, moreover, that the num- 

 ber of lakes is greater than was supposed after Stanley's 

 mission, and Col. Gordon is making a careful survey of 

 the newly Egyptianised country. He has sent to M. 

 Daubr€e, Director of the School of Mines, some speci- 

 mens of gold and silver ores brought from the interior, 

 in order to ascertain their value. The Society has re- 

 cently received a detailed account of the expedition made 

 by MM. Cambier and Marno from Zanzibar during 

 the past winter. The journey lasted seven weeks, and 

 was accomplished without loss of life. The chief 

 object of this tour was to test the availability of the route 

 by Mpwapwa for expeditions into the interior of Equa- 

 torial Africa. It was found to be well adapted even for 

 waggons. 



The Italian Consul at Aden, who is now in Europe, 

 is occupied with the formation of a society for the 

 purpose of acquiring a portion of land and forming an 

 Italian colony at Shoa. The object of the colony is to 

 establish commercial relations between Italy and Central 

 Africa. The African traveller, Carlo Piaggia, is now 

 making the final preparations for a new journey to Equa- 

 torial Africa. This journey will be his fourth ; formerly 

 he has principally visited Abyssraia and Soudan. 



Mr. Gordon Bennett's polar expedition, to which 

 we have already referred, is not to start, it would seem, 

 till 1879, "when, in June, it will probably leave San Fran- 

 cisco for the route by Behring' s Straits. The Pandora, 

 which will be re-christened the Jeannette, is being 

 thoroughly refitted in Walker's yards on the Thames. 



