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NATURE 



[August 23, 1888 



The heliometer is at present engaged on a triangulation of 

 stars near the North Pole for Prof. Pickering, but the last three 

 months of the present year it is to be employed in the deter- 

 mination of the solar parallax during the extremely favourable 

 opposition of Iris. Measures of the diameters of the sun and of 

 Mars, measures of certain double stars, the investigation of the 

 parallaxes of 6 B Cygni, and of 181 15/22 Lalande, are amongst 

 the other labours of the Observatory. Mr. Hall has nearly 

 completed the reduction of his measures of Titan. 



Gravitation in the Stellar Systems. — Prof. Asaph Hall 

 supplies an interesting paper on " The Extension of the Law of 

 Gravitation to Stellar Systems," in Gould s Astronomical Journal, 

 No. 177, towhichDr. Elkin's new value of the parallax of Arcturus 

 mignt afford a most striking illustration. Prof. Hall shows that 

 there is a theoretical difficulty in proving the law of Newton for 

 double stars which we cannot overcome, though the probability 

 of the existence of this law can be increased as more double 

 star orbits, and those very differently situated, are determined. 

 Still, even then, before the universality of the law can be 

 inferred, there remains the difficulty of the so-called "runaway " 

 ■stars, like Groom bridge 1830, stars moving through space with 

 the speed of a comet at perihelion, and yet with no visible 

 attracting body near them. Of these Prof. Hall supplies a list. 

 But if Dr. Elkin's value of the parallax of Arcturus be accepted, 

 that star would outstrip any of those given in this table. For 

 its speed in the direction at right angles to the line of sight 

 would be 373 miles per second, a speed compared with which 

 its speed in the line of sight, as given by Dr. Huggins, 55 

 miles per second, becomes small. Prof. Hall concludes, there- 

 fore, that though Newton's law is one of the greatest generaliza- 

 tions of science, it is better and safer "to await further 

 knowledge before we proceed, as Kant has done, to construct 

 the universe according to this law." 



ASTRONOMICAL PHENOMENA FOR THE 



WEEK 1888 AUGUST 26— SEPTEMBER 1. 

 /"C*OR the reckoning of time the civil day, commencing at 



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

 is here employed. ) 



At Greemvich on August 26 

 Sunrises, 5h. 5m. ; souths, I2h. im. 28*95.; sets, i8h. 57m. : 

 right asc. on meridian, ioh. 22 - im. ; deck id 3 11' N. 

 Sidereal Time at Sunset, 17I1. 19 m. 

 Moon (at Last Quarter August 29, I4h.) rises, 2oh. 54m.* ; 

 souths, 3I1. 22m. ; sets, ioh. 2m. : right asc. on meridian, 

 ih. 4i - 6m. ; decl. 5° o' N. 



Right asc. and declination 

 Planet. Rises. Souths. Sets. on meridian. 



h. m. h. m. h. ni. h. m. „ , 



Mercury.. 5 14 ... 12 13 .. 19 12 ... 10 33*8 ... 10 52 N. 



Venus ... 6 14 ... 12 51 ... 19 28 ... 11 u - 5 ... 6 42 N. 



Mars ... 12 27 ... 16 48 ... 21 9 ... 15 9-6 ... 19 12 S. 



Jupiter... 13 2 ... 17 23 ... 21 44 ... 15 44-5 ... 19 S S. 



Saturn ... 3 6 ... 10 43 ... 18 20 ... 9 35 ... 17 33 N. 



Uranus... 8 59 ... 14 35 ... 20 11 ... 12 56*1 ... 5 20 S. 



Neptune.. 21 56*... 5 43 ... 13 30 ... 4 2-3 ... 18 59 N. 



* Indicates that the rising is that of the preced.ng evening. 



Variable Stars. 



Star. R.A. Decl. 



h. m. „ t h. rr.. 



R Arietis 2 9-8 ... 24 32 N. ... Aug. 26, M 



R Ceti 2 20 - 3 ... o 41 S. ... ,, 27, M 



A.Tauri 3 545 ... 12 10N. ... ,, 27, 22 41 m 



TT ^ . " 31, 21 33 m 



U Monocerotis ... 7 25-5 ... 9 33 S. ... ,, 27, m 



R Virginis 1232-8... 7 36 N. ... „ 31, M 



S Bobtis 14 19-1 ... 54 19 N. ... ,, 27, M 



* Librae 14 55-0 ... 8 4 S. ... ,, 30, 22 8 tn 



W Scorpii 16 5*2 ... 19 51 S. ... ,, 28, M 



W Ophiuchi ... 16 15-4 ... 7 26 S. ... ,, 28, M 



R Draconis 16 32^4 ... 67 o N. ... ,, 30, M 



U Ophiuchi 17 10*9 ... 1 20 N. ... ,, 30, o 2S m 



,, 30, 20 36 m 



W Sagittarii ... 17 57-9 ... 29 35 S. ... ■ ,, 27, o o M 



Z Sagittarii 18 14-8... 18 55 S. ... ,, 27, 1 o M 



,, 31, o O m 



U Sagittarii' 18 25-3... 19 12 S , 26, o oM 



U Lyrae 18 46-0 ... 33 14 N. ... ,. 26, 1 o ;;/., 



R Aquilae 19 10... 8 4 N. ... ,, 29, m 



X Cygni 20^39-0 ... 35 11 N. ... Sept. 1, 3 o m 



M signifies maximum ; m minimum ; m 2 secondary minimum. 



Occultation of Star by the Moon (visible at Greenwich). 



Corresponding 



angles from, ver- 



Aug. Star. Mag- Disap. Reap. tex to right for 



inverted image, 

 h. m. h. m. no 



26 ... £ J Ceti 4 ... 23 20 ... o 22t ... 98 238 



t Occurs on the following morning. 



Meteor- Showers. 



R.A. Decl. 



6 ... 11 N. ... Swift. 



•• 30 •■• 35 ^ T - 

 • 3°5 ■•• 54 N. ... Swift, bright. Sept. I. 



.. 336 ... 58 N. ... Swift. 



Near £ Trianguli 



» 33 Cygni 

 ., 5 Ceohei 



GEOGRAPHICAL NOTES. 



The Times printed on Tuesday the substance of communica- 

 tions received from Mr. Joseph Thomson, dated from the city of 

 Morocco, July 22. Mr. Thomson writes in the highest spirits, 

 and with evident satisfaction at the results he has so far attained ; 

 for much of the country through which he has had to pass is in 

 a state of rebellion, and the local authorities have done more to 

 hinder than to help him. Mr. Thomson sailed from Tangier to 

 Casablanca, and thence travelled overland to Mogadon After 

 three weeks' preparation there he made his final start, and. as lie 

 states, soon discovered that the greatest danger to his success 

 would not be the mountaineers nor even the opposition of the 

 Government officials, but the half-dozen men who formed the 

 personnel of his small party. Mr. Thomson's past experience in 

 Africa enabled him to deal effectively with this difficulty. By a 

 series of surprises and cleverly-planned excursions he has been 

 able to enter the mountain fastnesses of Morocco and do more 

 than any previous traveller has done. From Demnat he made 

 two extremely interesting trips into the lower ranges, vi>iting 

 some remarkable caves and equally remarkable ruins, and one of 

 the most wonderful natural bridge-aqueducts in the world. Geo- 

 logically and geographically these trips are alike important. They 

 were followed by a dart across the main axis of the Atlas to the 

 district of Tiluit, which lies in the basin of the Draa. Here he 

 spent a very delightful ten days, though virtually a prisoner. As 

 the tribes further west on the southern slope were in revolt, Mr. 

 Thomson was compelled to return to the northern plains. 

 Starting once more, he crossed the mountains by a pass a little 

 south of Jebel Tizsm, ascended by Hooker, and reached Gindafy 

 safely. He was able to make a trip up a wonderful canon, 

 which he declares rivals those of America for depth and grandeur, 

 and ascended a mountain, where he and his party were confined 

 to their tents until it suited them to go back to their starting- 

 point. Here, unfortunately, Mr. Thomson's young companion, 

 Mr. Crichton Browne, was stung by a scorpion, and they were 

 compelled to return, happily by a new route. Though laid up 

 for a period, fortunately in time Mr. Crichton Browne recovered. 

 From his previous starting-point Mr. Thomson scored another 

 great triumph. He crossed the mountains once more, and 

 ascended with no small danger and difficulty the highest peak of 

 the Atlas Range north of Amsiviz, a height of 12,500 feet — the 

 highest peak, by 1500 feet, ever attained. This he describes as 

 the most interesting of all his trips, and he enjoyed it thoroughly, 

 though he had to sleep on the ground and was glad to make a 

 meal on walnuts. On his return, Mr. Thomson deemed it 

 advisable to go into the town of Morocco to recruit and wait the 

 arrival of further supplies from the coast. He intended to 

 resume work in a few days after the date of his letter. He 

 proposed first to make for the Urika River and penetrate the 

 mountains up its course. He will then work his way round to 

 Mogador, which hs expects to reach about the end of August. 

 There probably his work of exploration will end, though he may 

 make one Or two short trips into the interior and down to Agadir. 

 The return route to Tangier will probably be from Mogador to 

 the city of Morocco, thence to Mazagan on the coast, and on to 

 Casablanca and Rabat. Then he will leave the sea again and go 

 to Mequinez and Fez, reaching Tangier about the end ot the 

 year. The Times understands that his contributions to various 

 branches of science, especially to botany, will be of the highe 

 value. 



A LETTER from Cayenne to the Temps states that 

 Coudreau, who has recently explored Guiana, arrived there last 

 month after having travelled for eleven months in the wester 

 range of the Tumuc-Humac Mountains, between the sourc 



: 



last 

 western 

 ource of 



