226 



NATURE' 



IJuly 3, 1879 



worded definitions to separate the sub-kingdoms, classes, 

 and sub-classes of the vegetable kingdom. Modem re- 

 search is now all destructive, nor seems it to have a 

 thought as yet of proceeding on the lines of scientific con- 

 struction. E. Perceval Wright 



OUR ASTRONOMICAL COLUMN 



Olbers' Comet of 1815.— The Royal Society of 

 Sciences of Haarlem have offered a prize for a new de- 

 termination of the elements of this comet, founded upon 

 the whole series of observations which remain in a form 

 admitting of more accurate reduction than they have yet 

 received, by the use of improved positions of the com- 

 parison stars and a calculation of the effect of perturba- 

 tions, while the comet was visible, with the more precise 

 values of the planetary masses which we now possess. 

 Bessel, in his final memoir upon this comet, not only in- 

 vestigated the elements of the orbit from the ensemble of 

 the observations in the form in which they were known 

 to '.him in 1815, but essayed to determine the effect of 

 planetary attraction upon the epoch of next return to peri- 

 helion, which he fixed to February 9, 1887, but he found 

 that the period of revolution resulting from the observa- 

 tions in 181 5, was liable to a probable error of ± loi days. 

 Unless the semi-axis major admits of determination 

 within narrower limits, a recomputation of the perturba- 

 tions would lose much of its value and interest, and 

 accordingly the Haarlem Society, in stating the terms of 

 the prize, limit the investigation now demanded to a 

 definitive calculation of the orbit of the comet in 

 1815, at least we so understand the notification in 

 Jlstronomische Nachrickten,lio. 2,264. Allusion is made to 

 Nature, vol. xix. pp. 268, 366, where we gave references 

 to publications in which the observations of this comet 

 that admit of a new reduction are to be found. The 

 Society at the same time offer a prize for a critical exami- 

 nation of Serpieri's theory of the zodiacal light, "especially 

 if it is to be sought within or without the earth's atmo- 

 sphere," and it does not clearly appear from the article 

 in the Astronomische Nachrichten, whether one prize is 

 intended to apply to the two subjects ; we can hardly 

 suppose that this is the case, as it seems unlikely that any 

 one person would engage upon problems of so widely 

 different a character. 



The New Comet. — The elements of the comet dis- 

 covered by Mr. Lewis Swift do not bear resemblance to 

 those of any comet previously computed, and it does not 

 appear that the body is one of any special interest. The 

 perihelion passage took place towards the end of April, 

 and the comet is now slowly receding from the earth. 

 From the direction of its path, so far as position is con- 

 cerned, it might remain visible for a considerable time, 

 but its brightness is stated to be sensibly diminishing. 



The Comet 1739 (III.).— The following orbit of this 

 comet by Mr. Hind rests upon a new reduction of some 

 of the observations made at Paris, and upon Cassini de 

 Thury's last observation as given by Pingrd. 



Perihelion passage, 1759, Dec. l6'84ioS G.M.T. 



O I II 



Longitude of perihelion 138 28 35 j Mean equinox 



,, ascending node ... 79 50 4 j 17600. 



Inclination 4 52 31 



Log. perihelion distance 9 •9848692 



Motion — retrograde. 



This is the comet which became suddenly visible in 

 Western Europe on January 8, 1760, when its distance 

 from the earth was within 0'075 of the earth's mean 

 distance from the sun. 



Variable Stars. — The following are Greenwich times 

 of geocentric minima of Algol according to Prof. Schon- 



feld's elements, from the middle of July to the middle of 

 October : — 



July 15 

 18 



Aug. 4 



7 



24 



The rise in brightness of Mira Ceti to its maximum on 

 September 11 may be well observed this summer. 

 S Cancri will be at a minimum on September 18 at loh. 4m. 

 On the variations of the latter star Schonfeld's memoir 

 published at Mannheim in 1872 may be advantageously 

 consulted. 



GEOGRAPHICAL NOTES 



The new number of the Geographical Society's periodi- 

 cal contains Mr. Keith Johnston's notes on " Native 

 Routes in East Africa, from Dar-es-Salaam towards Lake 

 Nyassa," accompanied by a very interesting map, in 

 which are embodied the particulars gleaned by Mr. 

 Johnston from native travellers. This paper is followed 

 by Prof. Geikie's lecture on geographical evolution, of 

 which an abstract appeared in Nature, vol. xix. p. 490, 

 and several pages are next devoted to a not very happy 

 attempt to present the salient geographical features of 

 Mr. Ryall's account of his explorations in Western Thibet, 

 which forms one of the appendices of the General Report 

 of the operations of the Survey of India for 1877-8. 

 Among the geographical notes we find intimations that 

 the science lectures are to be discontinued, and that the 

 Council have arranged to provide means of instruction 

 and training for intending travellers. There is also a 

 note of Mr. M. C. Doughty's visit to El-Hejjer, a reported 

 Troglodyte city in North-west Arabia, which disposes of 

 singular fables that have been accepted by some learned 

 Orientalists. 



The question of the availability of elephants in African 

 exploration, lately so much discussed, is now about to be 

 put to the crucial test of experiment. The four elephants 

 presented by the Indian Government to the King of the 

 Belgians for the use of his expedition have arrived safely 

 at Zanzibar, and have been landed near Dar-es-Salaam, 

 not, however, without some difficulty, as the following 

 extract from a letter written by a lady who witnessed the 

 scene will show : — " We never thought the first elephant 

 could get alive to shore. It swam more than a mile in 

 distance, and was in the water for more than an hour. 

 Long after it was half way it would keep turning round 

 and trying to come back to the ship. I cannot describe 

 to you the excitement there was on board. I fairly cried 

 once with anxiety and excitement, it would have been too 

 horrible to see it drowned! It tried to climb up the 

 ship's side once. It was pouring with rain, which made 

 things seem more dismal ; we were all wet through, but 

 nobody cared. We had to get our experience as we went 

 on, as no one knew anything about elephants on landing. 

 We managed the other three much better, and made the 

 Captain take the ship nearer in shore. Capt. Carter has 

 stayed over there to take the elephants to Dar-es-Salaam, 

 a distance of four miles, and will stay to see them com- 

 fortably settled." 



The Novoye Vremya gives some further news as to the 

 progress of the Russian traveller, CoL Prjevalsky. The 

 distance from the Saisan port to the River Buguluk, in 

 the southern Altai mountains, was accomplished by the 

 Colonel towards the end of April. All this tract is a 

 barren desert, having neither flora nor fauna, though the 

 banks of the River Urungu were found to bear some 

 slight vestiges of vegetation. As for the climate. Col. 

 Prjeralsky describes it as characterised by frost at night- 

 time, with heat and storms during the day. Eight degrees 

 of frost in the morning were often followed by 20 deg. of 



