398. Mr. Wuewe Lt on the Classification 
II. 7. Let pR’ and qgRm be the forms. In order that the 
obtuse edges of the pyramid gRm may replace the edges of the 
rhombohedron, we must have the axes coincident, and the base 
of a rhombohedron equivalent to pR’ must have its angles at 
those obtuse edges (at S, Fig. 1.). Or, increasing the linear dimen- 
sions of the rhombohedron in the ratio of OS to OC, or (see #). 
m 1 
3m-1 : 3m+1, its axis becomes © t 
oF ; into the axis of gRm. The 
3m-—1 H 3m+1 _ 3m+i 
5 qa. ence, pa= aves qa, p= Moy Waa q: 
axis of gRm is 
IV. 5. Let pRm and qR’'n be the forms. If we suppose the 
angle which the acute terminal edge of pRm makes with the axis 
to be the same as the angle which the obtuse terminal edge of 
gk’n makes, and the forms to be in a transverse position, it is 
manifest, that the faces meeting at the last-mentioned edge will 
truncate the faces meeting at the former edge, and will make 
parallel edges of Sac aan Now, the tangents of these angles 
Sieh 2 
e ——— —_ and 
3m+1 pa an LS 
(see I): and these will be equal if 
(3m + 1)p=(3n—-1) q. 
Hence, we have these corresponding values of these indices : 
BS m=3, 5, mi ee m=2, 3, 4 a we 
g=2) n=2, 3, 4)) q=1) n=5, 7, 5 q=5) n=2))° 
V.1. Let pRm, gRr be the forms. In the isosceles Sess 
gRr, the tangent of the angle which the terminal edge makes with 
the axis, is : OF (Fig. 1.). Therefore, in order that the obtuse 
terminal edges of pRm may truncate these, we must have (see /) 
1 OB By Obs .: 
OV) Gap OK? we ae 
