CAMBRIDGE : PRINTED BY J. AND C. F. CLAY, AT THE UNIVERSITY PRESS. 
570 
NOTES AND REFERENCES. 
and the formula 
enables this to be written in the definitive form 
d 
db da 
d , fdb 
dx dx 1 v 1 * Ty* dP + dy Ä. M57. + sJ + * 131 \ l jd - 
da 
dy \dy dx. 
d (, db 
We have 
dx (\p + c)+dy 
db 
dy 
7 da 
dx -=- 
dx 
d 
dz V cZy/ dz 
7 ¿6 
+ efo -7- = 0, 
dz 
da 
+ dy (±p + c) + dz dz = 0, 
and thence eliminating dx, dy, dz, we have 
d j f^ 4 db da\ 
dx V dy dx) ’ 
%p + c 
da 
dx 
d j fdb _ e?a\ 
dy \dy ' dx) ’ 
db 
dy 
ÌP + c 
which defines the triply orthotomic system. 
END OF VOL. VIII. 
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