366 O. C. Marsh on Ledererite frem Nova Scotia. 
: 6. As the oxygen of the bases should have to 
that of the silica the ratio of 1:2, all 
the basis of the sum total of the first analysis, it becomes ev- 
ident that the real composition of Ledererite, thus determined, 
is as follows :-— 
ait RR gag ioe yg Nye agen peer 47°19 
Ai See cs er Oe ess ee 20°13 
ae eS PSE A 744 
Ota er. SONNE SG RG WES "91 
POR FS CSI) NDS Oo aN 3°54 
Pee, os ie ares cuca = oi. 20°53 
99°74 
These results give the oxygen ratio of 1: 3:8: 6, and indi- 
eate for the mineral the formula (¢Na+jCa)$i+3isi?+6H, thus 
clearly establishing its identity with Gmelinite. In chemical 
consitution it differs from the normal Gmelinite only in having 
& considerable part of the soda replaced by lime, resem 3 
bet P es the variety from Antrim, Ireland, analyzed by CoB- 
The fact that crystals of this Gmelinite from Cape Blomi- 
don contained 12°37 per cent of silica as an impurity is @ Very 
: i ring on the paragenesis 0 
explanation it s 
