Feb. 14, 1889] 



NA TURE 



379 



elements for each of the four periods of observa'.ion. Then fel- 

 low the computations of the perturbations exercised by the 

 different planets from Venus to Uranus, Mercury having no appre- 

 ciable disturbing; effect, for the comet at perihelion does not come 

 far within the orbit of the earth, and remains well without that of 

 Venus, its perihelion distance being 0*83 1. The perturbations ex- 

 ercised by Jupiter, however, are most important, for the aphelion 

 of the comet does not lie far outside the orbit of that planet, 

 and the two tend to come into proximity every eleven years, 

 their aphelion distances being, respectively, 5*57 and 5*20, and 

 their periods 207679 and 4332*59 days, so that the comet was 

 only 0'87 distant from the planet in December 1870, and eleven 

 years later, in November 1881, wasonly half as far from it. These 

 perturbations were computed for intervals of twenty days through 

 the whole period covered by the observations, including thus 

 five revolutions ; and where it seemed desirable, for every ten or 

 even every five days. The reciprocal of the mass assumed 



for Tiipiter was - = 1047 '54, and with this value, so far from 



in 

 finding an acceleration of the mean motion of the comet, as 

 with Encke's comet, a retardation was displayed — a retardation 

 which, however, disappeared when a somewhat higher value 

 viz. 1047-1752, was substituted. It appears that this latter 

 value satisfies the observations not only of the comet in ques- 

 tion, but also those of Faye's and Encke's. The value obtained 

 by Dr. Schur from the four satellites of Jupiter doei not greatly 

 differ from that now found by Dr. von Ilaerdtl, and the latter 



considers that the simple mean of the two, - = 1047 204, may 



be adopted as the nearest approach to the true mass of Jupiter, 

 i.e. of the Jovian system, the satellites being included. 



ASTRONOMICAL PHENOMENA FOR THE 



■ WEEK iZZc) FEBRUARY \7 -21. 



/pOR, the. reckoning of time the civil day, commencing at 

 ^ Greenwich mean midnight, counting the hours on to 24, 



H here employed.) 



At Greenwich on February 17 

 Sun rises, 7h. iim. ; souths, I2h. 14m. I2"03. ; sets, I7h. 17m. : 

 right asc. on meridian, 22h. 4'9m, ; decl. 1 1° 48' S. Sidereal 

 Time at Sunset, 3h. 8m. 

 Moon (at Last Quarter on February 23, oh.) rises, I7h. 59m.* ; 

 souths, ih. 12m. ; sets, 8!i. lom. : right asc. on meridian, 

 iih. 0'9m. ; decl. 10° 42' N. 



Right asc. and declination 

 Planet. Rises. Souths. Sets. on meridian. 



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



Mercury.. 6 37 ... 11 49 ... 17 i ... 21 397 ... 10 6 S. 



Venus 8 22 ... 15 4 ... 21 46 ... o 55-6 ... 7 42 N. 



Mars 8 9 ... 14 11 ... 20 13 ... o i-6 ... o 26 S. 



Jupiter.... 4 24 ... 8 19 ... 12 14 ... 18 8"8 ... 23 6 S. 

 Saturn.... 15 47 ... 23 22 ... 6 57*... 9 14-9 ... 17 11 N. 

 Uranus... 22 8*... 3 32 ... 8 56 ... 13 214 ... 7 53 S. 

 Neptune.. 10 16 ... 17 59 .. i 42*... 3 50-9 ... 18 26 N. 

 * Indicates that the rising is that of the preceding evening and the setting 

 that of the following morning. 

 Feb h. 



18 ... 4 ... Venus at greatest elongation from the Sun, 

 47° east. 



Variable Stars. 

 Star. R.A. Decl. 



h. m. „ . h. m. 



U Ccphei o 52-5 ... 81 17 N. ... Feb. 17, 19 9 »» 



,, 22, i8 49 m 



R Ceti 220-4... o 41 S. ... ,, 17, M 



A.Tauri 3 546 ... 12 11 N. ... ,, 17, 18 32 m 



R Canis Majoris... 7 14-5 ... 16 11 S. ... ,, 17, 2 39 m 



and at intervals of 27 16 



U Monocerotis ... 7 25-5 ... 9 33 S. ... Feb. 20, ' M 



S Canis Minoris ... 7267... 8 33 N. ... ,, 22, m 



S Cancri 8 376 .. 19 26 N. ... ,, 20, 19 22 m 



U Hydrje 10 32-1 ... 12 48 S. ... ,, 22, M 



R HydrK 13 237 ... 22 42 S 17, M 



R Lyrae 18 52-0 ... 43 48 N. ... ,, 18, m 



U Cygni 20 162 ... 47 33 N. ... ,, 20, M 



X Cygni 20 390... 35 11 N. ... ,, 18, 2 oM 



4 Cephei 22 25*0 ... 57 51 N. ... ,, 19, o o /I/ 



M signifies maximum ; ;// minimum. 



Meteor-Showers. 

 B.A. D(cl. 



From Canes Venatici ... i8j ... 34 N. 



Near t Herculis 238 ... 46 N. 



,, p Herculis 260 ... 36 N. 



February 20. Very 



swift ; white. 

 February 17. 

 February 20. Swift. 



GEOGRAPHICAL NOTES. 

 \ A PAPER of more than usual interest was read at Monday's meet- 

 ! ing of the Royal Geographical Society, by the Rev. W. Spotswood 

 j Green, on his explorations in the glacier regions of the Selkirk 

 Range, British Columbia, in the summer of 1888. This range 

 is generally included in the Rocky Mountains, although, as Mr. 

 Green showed, it is in many respects distinct from them. After 

 crossing the Rockies by the Canadian Pacific Railway, and 

 i plunging into the valley of the Columbia River, the Selkirk 

 I Range lies before the traveller. It has been but little explored, 

 I and some of its glaciers were probably visited for the first time 

 I by Mr. Green. The Selkirk Range is entirely bounded by the 

 I great bend of the Columbia and its tributary, the Kootenie, and 

 the drainage of all its glaciers finds its way into the Columbia in 

 some part or other of its course. Under many difficulties, owing 

 to the densely forest clad nature of the ground, the want of 

 guides and porters, the necessity of opening up new routes, and 

 other causes, Mr. Green visited some of the higher parts of 

 the range, and explored, and in some cases named, its pre- 

 viously unvisited glaciers. After crossing the Rockies proper, 

 curiously ridged prairie hills have to be parsed, and all the 

 ranges between these and the Columbia have a smooth rounded 

 outhne, forming a strong contrast to the ranges on the other side 

 of the watershed. These latter form a complexity of glacier-clad 

 ranges, many peaks rising quite as high as those on the watershed. 

 Among the higher ranges an immense number of small glaciers 

 lie in the hollows, and two extensive snow-fields are to be found 

 within the limits of Mr. Green's map. One of these, being the 

 source of the best-known glacier in the whole region, on account 

 of its being so clearly visible from the railway, Mr. Green has 

 called the great lUecellewaet firn, after the river of which it is 

 the true source. This ice-field, probably 500 feet thick, to the 

 southward extends down into a valley as the Geikie Glacier, 

 and to the eastward, having been joined by ice-streams coming 

 from the Dawson Range, it pours into Beaver Creek Valley as 

 the Deville Glacier. All these glaciers show evidence of 

 shrinking. An immense moraine exists in the valley 

 below the lUecellewaet Glacier. Some of the blocks of 

 quartzite in the moraine are of huge dimensions, one 

 being 50 feet long, 24 feet thick, and 33 feet high. 

 Mr. Green set up some poles at a little distance from the end of 

 the glacier, and found that after thirteen days the ice had 

 melted a vertical foot over its whole surface, and the centre of 

 the glacier had moved 20 feet. The Geikie Glacier, about 4 

 miles long and looo yards wide, is a much more interesting ice- 

 stream. Sheltered from the sun's rays by high clifTs, it flows 

 along a level valley, so that one can walk across its lower portion in 

 various directions without trouble. As it descends from the firn, it 

 is much broken ; then its surface becomes level, but with numerous 

 transverse crevasses. Flowing round abend, longitudinal fissures 

 are set up, crossing the others, and forming such a multitude of 

 sJracs that the surface presents an appearance more like some 

 basaltic formation with the columns pulled asunder than any- 

 thing else I can think of. This beautiful structure gives place 

 to the frozen waves of a iner de glace, and the glacier terminates 

 in longitudinal and slightly radiating depressions and crevafses. 

 The level of perpetual snow in these mountains may be put 

 down at 7002 feet, and the upper limit of the forest at 6000 feet. 

 I Red snow, caused by the presence of Protococcus nivalis, is of 

 I frequent occurrence. Like most of the rest of British Columbia, 

 j the Selkirks are covered with forests, all the trees attaining 

 I huge dimensions. These forests are being devastated by fires, 

 I often caused by sparks fro;n the engines on the new railway. 

 Beneath the living trees, thousands of prostrate trunks lie piled 

 in every conceivable position, and in every stage of decay. 

 Exploration and mountaineering under such circum-tances 

 are attended with enormous difficulties. Above the forest 

 I region, the slopes of the mountains are as profusely covered 

 ' with flowers as the " Alp " region of the Swiss mountains ; the 

 most conspicuous plant being the Castilleia miniata. The he^ps 

 [ of boulders above the forest region form a refuge for a great 



