yune 20, 1889] 



NATURE 



181 



'f The second remarkable conjunction will be that of lapetus, the 

 outermost satellite of Saturn, with Titan. This will occur on 

 November i at 8h., and the two satellites, moving in different 

 directions, will pass within 3" of each other. Shortly after this 

 close approach lapetus will enter the shadow of the ring system, 

 and as Saturn is then near quadrature, the entire passage of the 

 satellite through the shadow will be clear of the planet as seen 

 from the earth. The satellite's path traverses the shadow of the 

 rings on both sides of the planet, and the clear space between the 

 planet and ring on one side, but probably not on both. It will 

 be a matter of the greatest interest and importance to note if the 

 satellite shines out when crossing the projection of the Cassinian 

 division, and if it is at all visible when in the shadow of the 

 dusky ring or crape veil. The Australian astronomers will have 

 the opportunity, if weather serves, of observing this most rare 

 and interesting occurrence, whilst those of America will be best 

 able to observe the first-named conjunction, viz. that of Saturn 

 and Mars. 



The General Relations of the Phenomena of 

 Variahle Stars. — Under this title Mr. S. C. Chandler, who 

 has in such an especial manner made the subject of variable stars 

 his own, contributes to Gould's Astronomical Jotirnal, No. 193, 

 the results of his discussion of the facts as yet ascertained with 

 relation to these objects. Making abstraction of the stars of the 

 Algol time, it appears that variables may legitimately be divided 

 into two great classes, those of short and those of long period ; 

 the former including the stars of less than 90 days' period, 

 the latter those of more than 120 days. The first characteristic 

 related to the length of period is that of colour — ^" the redder 

 the tint, the longer the period." The range of variability is 

 another feature. This also appears to depend upon the period — 

 the greater the range, the longer the period- — but the relation is 

 not one of simple proportionality. The form of the light-curve 

 is a third point. For the short- period variables the time of in- 

 crease averages about two-thirds the time of decrease, but for the 

 long-period stars the rate varies in a curious manner. Increase 

 and decrease take about the same time for stars, between 100 and 

 2CO days ; then the ratio lessens, until for stars of about a year's 

 period the time of increase is only about half that of increase ; 

 the ratio then increases again, and for the stars of longest .period 

 decline and recovery proceed with about equal speed. It is also 

 noteworthy that though it would appear that stars with a period 

 of a year or nearly a year are less likely to be readily discovered 

 than those of a longer or shorter variation, yet as a matter of 

 fact they form distinctly the most numerous class of the long- 

 period stars. Both these curious facts stand as yet without 

 explanation. 



A point of difference between the long-period and short- 

 period stars appears to be indicated in the irregularities to which 

 their periods are severally subject ; the irregularities in the first 

 case being, broadly speaking, periodic in their nature, but in 

 the second case secular, or at all events requiring very many 

 cycles of the star for their development. These irregularities 

 are common for the first class, but quite exceptional for the 

 second. For these reasons, and considering the absence of 

 stars of between 90 and 120 days, the difference in colour in 

 average range of variation, and in form of light curve between 

 the two classes, Mr. Chandler is led to believe that the cause of 

 variation is probably different for the two classes of stars, as it 

 is probably different again for the third class we call after 

 Algol. With regard to the distribution of variables, Mr. 

 Chandler shows that our present knowledge is insufficient to 

 justify any very substantial inferences. A certain aggregation 

 of short-period variables near the plane of the Milky Way does, 

 however, seem to be indicated with some distinctness. 



ASTRONOMICAL PHENOMENA FOR THE 



WEEK 1889 JUNE 11-1^. 

 /T7OR the reckoning of time the civil day, commencing at 

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



is here employed.) 



At Greefiwich on June 23 

 Sun rises, 3h. 45m. ; souths, I2h. im. 57"is. ; daily increase of 

 southing, 12 '95. ; sets, 20h. 19m. : right asc. on meridian, 

 6h. 9"3m. ; decl. 23° 26' N. Sidereal Time at Sunset, 

 I4h. 28m. 

 Moon (New on June 28, 9h.) rises, ih. 29m. ; souths, 

 8h. 19m. ; sets, I5h. 23m. : right asc, on meridian, 

 2h. 25 •3m. ; decl. 9" 21' N. 



Right asc. and declination 

 Planet. Rises. Souths. Sets. on meridian. 



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



Mercury.. 3 49 ... ii 36 „, 19 23 ,„ 5 43-6 ... 18 57 N. 



Venus I 41 ... 8 58 ... 16 15 ... 3 4-5 .,, 13 56 N. 



Mars 3 33 ,.. II 55 ... 20 17 .,, 6 27 .,, 24 11 N. 



Jupiter,.,. 20 16*... o 10 ... 4 4 ... 18 15-8 ,,. 23 14 S. 



Saturn,... 7 41 ... 15 13 ... 22 45 ... 9 2i*o ... 16 42 N. 



Uranus... 13 27 ... 18 58 ... o 29*... 13 6-9 ... 6 26 S. 



Neptune.. 2 11 ... 9 59 .. 17 47 ... 4 57 ... 19 13 N. 

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



setting that of the following morning. 



June. h. 



24 ... 6 ... Venus in conjunction with and 1° o' north 



of the Moon. 

 24 ... 19 ... Jupiter in opposition to the Sun. 



26 ... 7 ... Venus at greatest distance from the Sun. 



27 ... 8 ... Mercury in conjunction with and 3° 4' south 



of the Moon. 



28 ... 3 ... Mars in conjunction with and 1° 32' north 



of the Moon. 

 28 ... 9 ... Annular eclipse of the Sun : visible princi- 

 pally in the southern portions of Africa. 



Variable Stars. 

 Star. R.A. Decl. 



h. m. o / h- m. 



U Cephei o 52*5 ... 81 17 N. ... June 24, 22 27 m 



,, 29, 22 6 m 



8 Librae 14 55*1 ... 8 5 S. ... ,, 24, 20 50 m 



U Coronse 15 137 ... 32 3 N. ... ,, 26, o 58 w 



V Herculis 16 54-2 ... 35 14 N. ... ,, 26, M 



U Ophiuchi 17 iO"9 ... i 20 N. ... ,, 27, 2 26 m 



,, 22 34 m 



X Sagittarii 17 406 .. 27 47 S. ... ,, 23, 22 oM 



,, 28, I o m 



U Sagittarii 18 25*6 ... 19 12 S. ... ,, 29, i o m 



3 Lyrse 18 46'0 ... 13 14 N. ... ,, 25, 22 o m 



,, 29, 3 o M 



1) Aquilae 19 468 ... o 43 N. ... ,, 25, 21 o m 



T Aquarii 20 44'l ... 5 34 S. . ,, 23, m 



M signifies maximum ; tn minimuni. 



Meteor-Shower.' 

 R.A. Decl. 



Near 52 Herculis 

 ,, 5 Cygni ... 

 ,, 6 Delphini 



254 

 295 

 305 



47 N. 



40 N. 



9 N. 



Swift. 

 Slow. 

 June 28. 



GEOGRAPHICAL NOTES. 



The recent telegrams relative to Mr, Stanley's movements 

 cannot be regarded as satisfactory. There can be no doubt that 

 he has reached the east coast of the Victoria N-yanza, but that 

 he could do so in eighty-seven days from Yambuya, on the 

 Aruwimi, is incredible. Therefore the date, December 2, as 

 that on which Mr. Stanley was at Ururi, on the southeast of 

 Victoria Nyanza, must be wrong. Moreover a message would 

 not take six months to reach Zanzibar from there ; the journey 

 in normal times can be done in one month. It is to be feared 

 that Mr. Stanley has had to leave the problems connected with 

 the Mwuta Nzige unsolved. It would seem as if he had come 

 round by the country to the north of Uganda, and so reached the 

 Nyoro country on the north-east of Victoria Nyanza. After 

 Emin received all the stores which Stanley took back with him 

 (from Mslala on the south of Victoria Nyanza), the probability is 

 that the Pasha would return to Wadelai. However, it is expected 

 that a letter from Mr. Stanley will arrive in a few days. 



Dr. Frithjof Nansen arrives in London to-morrow, and 

 during his stay will be the guest of Prof Flower. 



The June number of the Scottish Geographical Magazine is a 

 particularly good one. Mr. H. B. Guppy contributes the first 

 part of the results of his observations on the Cocos-Keeling 

 Islands, which promise to be an important addition to the 

 already abundant literature on the formation of coral islands. 

 Mr. Guppy also sends an interesting short paper on Tridacna 

 pearls. Mr. W. B. Tripp's notes on South American rainfall 

 .south of the tropics are useful. Dr. H. R, Mill contributes a 

 highly suggestive paper on scientific earth-knowledge as an aid 

 to commerce. Dr. Mill really indicates the lines on which the 



