182 



TROY. W. J. SOLLA'S ON 



[May 



l 9°3>. 



circular form are those of the East Indies and the Aleutian Isles. 

 If we sweep a great circle to pass through the centres of these, it 

 will be found to run symmetrically through the bordering seas of 

 Asia as far as Alaska, traversing the centre of the Japanese arc on 



Kg. 1. 



Stereog raphic projection of the Earth, the pole of projection 6 C north of the 

 Equator in the Eastern Hemisphere. 



The great circles indicated by thin continuous lines are a system of three, 

 having their points of intersection 90° apart, and one of which passes through the 

 centres of the East Indian and Aleutian arcs. The great circles distinguished by 

 crossed lines j j j are a similar system, and one of them passes through the centre 

 of Suess and the East Indian centre. The great circles shown by thick continuous 

 lines are a third similar system, and one of them passing through the East 

 Indian centre bisects the angle formed by the other two great circles which pass 

 through the same centre. My best thanks are due to my friend Mr. H. N. 

 Dickson, who kindly constructed for me the network of circles of latitude and 

 longitude on which the stereographic projection is based. 



[The draughtsman has accidentally omitted the +Cau indicating the position 

 of the Caucasian centre in the above figure. It lies on the same circle as +S, 

 o ' crossbars ' north-west of it.] 



