AT THE UNIVERSITY’ PRESS. 
60 6 
NOTES AND REFERENCES. 
I may refer also to the Memoir, Sir It. S! Ball “ On the theory of the Content,” 
Trans. B. Irish Acad. vol. xxix. (1889), pp. 123—182, where the same difficulty is 
discussed. The opening sentences are—“In that theory [Non-Euclidian Geometry] it 
seems as if we try to replace our ordinary notion of distance between two points by 
the logarithm of a certain anharmonic ratio. But this ratio itself involves the notion 
of distance measured in the ordinary way. How then can we supersede the old 
notion of distance by the Non-Euclidian notion, inasmuch as the very definition of 
the latter involves the former ? ” 
An extensive list • of papers is given, Halsted, Bibliography of Hyper-Space and of 
Non-Euclidean Geometry, Amer. Math. Jour. t. I. (1878), 'pp. 261—276 and 384—385, 
also t. ii. (1879), pp. 65—70. 
END OF YOL. II. 
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