OF COPPPER-PYEITES. 
11 
S 
a P— 00. p. ^P. P+l. %. 14. It would have been 
impossible to derive from this combination, without 
other forms entering into it, the relation of g^P 
to P ; the pyramids of the subordinate occurring at 
the same time with P — 2 of the principal series in 
variety 7. afforded the data required for this deve- 
lopment. 
10. P-3. P+1. gJgP+l. P+ 00. fig. 15. 
(PL II.) 
11. P-2. g^P. P+1, g^gP+l. P+2. fig. 16. The 
most acute of these pyramids is the member subse- 
quent to that which appears with parallel edges of 
combination in the place of its terminal edges. The 
last member, from several varieties already mention- 
ed, is known to be P4-I ; and thus the new pyramid 
can be nothing else than P+S. 
Its axis is =\/S1.0592; 
terminal edge = 96° 3-3' ; 
lateral edge == 140° 31^ 
m p-oD. p~2. ^^p. p+i. g^^P+i- %• 
13. P-x. P~2. P. ^^P. gJ^P+l- fig. 18. 
14. ' P— 1. P. P+l. %. This combina- 
tion presents very distinctly the remarkable singu- 
