402 Mr. WHEWELL on the Classification 
RHOMBOHEDRAL SYSTEM. 
Example and Figure. Class. Combination. 
Class I. |pR,gR & pR,gR’ 
Rh’. Kouphone-spar. £R’,R| No. 1. oR R’ 
Mohs, Vol. II. 120. x P o"-'R’, "R 
pR, 2pR’ 
or 3pR’, pR 
Rh’. Lime-haloide R,4R] No. 2. oR, ot R 
II. 115. P m generally pR, gR 
Rh’. Alum-haloide OR, R| No. 3. OR, gR 
Loomer, 
This prism is distinguish- | Rh’. Lime-haloide R, oR | No. 4. pR, oR 
able from Rr in III. 4. TS 4 eee oc 
by the position of its faces. 
Class IT. pR,qRm 
and pR’, gRm 
Rh’. Lime-haloide R, R3 | No. 1. pR, pRm 
If. 116. “Pr 
OR, R3 | No. 2. OR, pRm 
Oo © 
The figure of the faces of | Rh’. Lime-haloide ©R,R5| No. 3. 
the prism shews it to be ®R, cy 
andnot © Rr, in which the te- 
tragons are rhombs, see V.4. 
No. 4 
Rh’. Ruby-blende+ R’, i R3 
LOR 3 
generally 
te: gk',qRm 
4 
