] x ii PRESIDENT'S ADDRESS. 



slu-xviiiL' that if the velocity were the same as that of light, 

 tin- moon's mean motion would be retarded a few seconds 

 of arc in a century. As a matter of fact there is a slight 

 acceleration, but that is presumably due to other 

 undetermined causes. The address of the President of 

 the sub-section Cosmical Physics at the British Association 

 is on the subject of the moon's motion, and also deals with 

 its past history. It was some time ago suspected that a 

 nebula in Virgo was rotating about a central axis ; this is 

 now shewn to be the case, the form of the nebula being a 

 spiral, seen edgewise. The motions of stars can only be 

 perceived by very accurate observations at considerable 

 intervals, but there is reason to believe that they have some 

 connection with the stage in evolution that each star has 

 reached and the group to which it belongs. This, if confirmed, 

 opens out a new and large field for inquiry. The difficulties 

 may be appreciated from the fact that the star with the 

 greatest proper motion only moves about a quarter of a 

 degree in a century, and nearly all are far slower. The 

 most striking comet visible in the past year was Delavan's, 

 which, though not a very large one, was well seen by the 

 naked eye for a long period in the neighbourhood of the 

 Great Bear. The tail was about 2 in length. Encke's 

 comet was also observed in October. This is a short period 

 comet, having a period of 3 years, its orbit lying within 

 that of Saturn. With regard to the variability of the sun's 

 heat , a connection has been traced between the mean monthly 

 radiation and the number of sunspots, an increase of the 

 latter corresponding with an increase of the former. The 

 various expeditions made to observe the total eclipse of the 

 sun on August 21st, 1914, were on the whole successful, 

 though some were greatly interfered with or stopped by the 

 condition of things in Europe. Two parties, from the 

 luirh Observatory and from the Royal and Royal 

 A-inmnmical Societies, in Russia and Sweden respectively, 

 ol.tiiim'd good photographs of the corona and other details. 

 The transit of Mercury which took place on November 7th, 



