340 
The specific gravity was 2-54, 
tion — - 
Silica, . . 44'21 
Peroxide iron, . 19 2 4 
Alumina, . . 23' 26 
Lime, . . 7' 64 
Magnesia, . . 2-34 
Soda, . . 2-57 
Potash, . . O' 95 
Iron, . . 031 
and the quantitative compos! 
Oxygen ratio as 1 : 1. 
Oxygen quotient, 0*87. 
100-52 
The body resembling felspar was next examined ; the crystals did 
not effervesce with acids, were easily powdered, and, when heated 
at the blow-pipe flame, they fused at the edges, and were easily 
marked with a knife. 
The specific gravity was 2*37, 
Silica, 
78-45 
Alumina, . 
13-39 
Lime, 
1-48 
Peroxideiron, 
1-31 
Potash, 
1-24 
Soda, 
4-90 
and the chemical composition : — - 
Oxygen ratio as 1 : 5. 
Oxygen quotient, 0'209. 
100*77 
From the above analysis, the substance most resembles albite or 
soda-felspar ; the excess of silica, and consequent reduction of the 
oxygen quotient, may be accounted for by the fact of its having 
undergone considerable weathering, and also that small quanities of 
quartz might have been associated with the specimen used for 
analysis. 
The sandstone forming part of the fort was of a coarse variety, 
and evidently, from its appearance, had been exposed to considerable 
heat ; it contained less silica than is usually found in building 
sandstones. 
Analysis afforded the following results: — 
Silica, 
68-80 
Peroxide iron, 
5-00 
Alumina, 
1915 
Lime, 
2-25 
Magnesia, 
0-60 
Potash, 
2*54 
Soda, 
1-66 
100-00 
