of Crystalline Combinations. 425 
Now if a be the axis, 6 and c the semi-diagonals of the fundamental 
form, the axis and semi-diagonals of gPm are respectively gna, nb, c. 
And hence, we have 
Cc 
eee 
qna a 
; whence g =i, n= 2. 
Since g makes horizontal edges with d, and d is 1P2, g is »P2. 
Hence, the expression for the form is 
LPP; $82, Pies Pr. ober olf, oP? 
Db ve? id c a fa ae 
o 
a: 
W. WHEWELL. 
Truity CoLLeceE, 
April 29, 1826. 
