Geological Society . 383 



either in magnitude or direction with that of j3 and y, which are 

 moving on absolutely parallel lines with equal velocity. 



There are many other interesting cases of the same kind. I hope 

 soon to be able to lay before the Society a pair of maps in which all 

 the well-recognized proper motions in both hemispheres are exhibited 

 on the stereographic projection. In the same maps also the effects 

 due to the solar motion are exhibited by means of great circles 

 through the apex of the solar motion, and small circles or parallels 

 having that apex for a pole. 



It appears to me that the star-drift I have described serves to 

 explain several phenomena which had hitherto been thought very 

 perplexing. In the first place, it accounts for the small effect which 

 the correction due to the solar motion has been found to have in di- 

 minishing the sums of the squares of the stellar proper motions. 

 Again, it explains the fact that many double stars which have a com- 

 mon proper motion appear to have no motion of revolution around 

 each other ; for clearly two members of a drifting-system might 

 appear to form a close double, and yet be in reality far apart and 

 travelling not around each other, but more closely around the centre 

 of gravity of the much larger system they form part of. 



I. may add that, while mapping the proper motions of the stars, 

 I have been led to notice that the rich cluster around x Persei falls 

 almost exactly on the intersection of the Milky Way with the great 

 circle which may be termed the equator of the solar motion — that 

 is, the great circle having the apex of the sun's motion as a pole. 

 This circumstance points to that remarkable cluster, rather than to 

 the Pleiades, as the centre of the sidereal system, if, indeed, that 

 system have a centre cognizable by us. When we remember that 

 for every fixed star in the Pleiades there are hundreds in the great 

 cluster in Perseus, the latter will seem the worthier region to be the 

 centre of motion. I should be disposed, however, to regard the 

 cluster in Perseus as the centre of a portion of the sidereal system, 

 rather than as the common centre of the Galaxy. 



The peculiarities of the apparent proper motions of the stars seem 

 to me to lend a new interest to the researches which Mr. Huggins 

 is preparing to make into the stellar proper motions of recess or ap- 

 proach. 



GEOLOGICAL SOCIETY. 

 [Continued from p. 315.] 



May 26th, 1869.— Prof. T. H. Huxley, LL.D., F.R.S., President, 

 in the Chair. 



The following communications were read : — 



1. " Notes on the Geology of Cape-York Peninsula, Australia.'' 

 By Alex. Eattray, M.D. 



The author stated that the Eastern mountain-range of Australia 

 is produced through and forms the axis of the peninsula of Cape 

 York; it consists of various granites and porphyries, gneiss, and 



