8 



NATURE 



[September 3, 1914 



conspicuous object in the night sky. In this chart 

 the observer is supposed to be looking due north, • 

 i.e. towards the pole star, the star being easily found 

 by the direction of the two pointers in the Great 

 Bear. If a vertical line be imagined drawn through 

 the pole star towards the horizon, then this line will 

 approximately pass through the comet at about ten 

 o'clock in the evening. While the comet has not a 

 great altitude, it is well above the northern horizon, 

 as shown in the chart. To the left of the comet is 

 the constellation of the Great Bear, and well to the 

 right (eastwards) is the constellation of Auriga with 

 the bright star Capella. It should not be forgotten 

 that, owing to the rotation of the earth, the constella- 

 tions have an apparent motion round the pole star, as 

 indicated by the arrows marked near the circles in 

 the chart. During the night, therefore, the stars and 

 the comet, as one faces northward, describe con- 

 centric circles round the pole star, and consequently 

 the stars under Polaris move from left to right. The 

 diagram thus clearly indicates that the later the comet 



mouth, with a prismatic camera of 12 in. aperture and 

 a 20° prism. 



Radial Motion in Sunspots. — The subject of the 

 radial motion in sunspots is referred to in three 

 communications to the July number (vol. xi., No. 1) 

 of the Astrophysical journal. The first is contributed 

 by Prof. W. H. Julius, and the position he takes up 

 is" " to defend the attacked position which is by no 

 means so weak as he represents it " in the criticism 

 of Mr. St. John of the anomalous dispersion theory 

 in explaining the observed phenomena. Space does 

 not permit one even to summarise Prof. Julius' con- 

 clusions, but it may be stated that the paper covers 

 thirty-two pages, and concludes with eleven para- 

 graphs of summary. The communications by Messrs. 

 Evershed and St. John deal with the question of the 

 limits of the radial motion. Mr. St. John's investiga- 

 tions indicated that the usual course of the displaced 

 lines over spots showed no sharp break, and the dis- 

 placement did not suddenly cease at the periphery of 

 the penumbra, but the line gradually returned to its 



<<-WC5r NORTHERN 



is observed, the higher above the horizon it will be 

 situated, and the best time to observe it is between 

 two o'clock and four o'clock in the morning. The 

 divided part of the smaller circle in the diagram shows 

 approximately the hourly apparent movement of the 

 stars. 



The comet is a naked eye object, and is a fine 

 sight as seen even with a pair of field glasses or a 

 small telescope. In the earlier part of the night, 

 when the comet is low down, the tail is nearly hori- 

 zontal, stretching out towards the east. As the morn- 

 ing approaches, the tail becomes more inclined, the 

 head then being at a lower altitude than the tail. 

 The comet has a very dense, almost stellar nucleus 

 and a considerable length of tail. On August 26 the 

 nucleus was estimated (visually) as being about mag- 

 nitude five, and the tail about one degree long, but on 

 August 28 the tail was judged to be equal to about four 

 lunar diameters, i.e. about two degrees in length, 

 and the nucleus of magnitude three. There is little 

 doubt that this object is being closely followed at all 

 observatories. Some good photograjjhs of the spec- 

 trum of the nucleus were secured during the early 

 mornings of last week at the Hill Observatory, Sid- 



NO. 2340, VOL. 94] 



HORIZON 



€AST-> 



normal course. Mr. Evershed's view is that there is 

 an appreciable break or jolt in the lines at the points 

 where they pass from the penumbra on to the sur- 

 rounding photosphere. The communications suggest 

 that these different views are to some extent one of 

 degree, and possibly due to the differences caused by 

 the instrumental equipment of these investigators. 

 Mr. St. John hopes to utilise the next maximum period 

 of sunspots to make a special examination of this 

 question, and a programme has already been planned. 



THE AUSTRALIAN MEETING OF THE 



BRITISH ASSOCIATION. 



SECTION C. 



geology. 



Opening Address by Prof. Sir Thomas H. Holland, 

 K.C.I.E., D.Sc, F.R.S., President of the Section. 



Exactly eighty-three years from the day of our 

 arrival at Sydney, Edward Suess was born in London. 

 Thus the day, as much as the circumstances of our 

 meeting so far from home, serves to remind us of one 

 who was great enough to recognise the fact that geo- 



