408 Mr. WHEWELL on the Classification 
RHOMBOHEDRAL SYSTEM. 
Remarks. Example and Figure. Class. Combination. 
Class _IV.| pRm, gR'n 
Rh’. Lime-haloide R3,2R’2| No. 5. pR’5, 2pR3 
pe pR3, 2pR 2 
2pR' 2, 2pR5 
generally, if 
(3m-+ 1) p 
=(32 -,1), 9. 
Class V. pRm, qRr 
pR3, 5pRr 
pR5, 8pRr 
generally, if 
(3 m+1)p=2q 
Rh', Iron-ore $R5, 2Rr No. 1. 
g 
R3,4Rr{ No. 2 pR3,4Rr 
if n pR5,7Rr 
| generally, if 
(3m—1)p=2q 
ORm, qRr 
pRm, oRr 
Rh’. Ruby-blende R3,®R} No. 4. 
Mohs, Vol. II. 126. x 
This position of the edges 
shews the prism not to be 
oR, as in II. 3. 
Rh’. Corundum 2 Rr, 4Rr 
II. 122. + b 
