606 
Proceedings of the Royal Society 
5, On the Formation of Serpentine from Dolomite. By J. J. 
Dobbie, M.A., D.Sc., Assistant to the Professor of 
Chemistry, University of Glasgow, and G. G. Henderson, 
B.Sc. 
Some time since, specimens of a peculiar-looking rock, found 
at Fintry, in the Campsie district, were put into our hands for 
analysis. The specimens were of a light chocolate-brown colour, 
and apparently homogeneous. They were somewhat harder than 
ordinary limestone, had a waxy lustre, and broke with a sharp- 
edged splintery fracture, translucent upon the thin edges. With 
hydrochloric acid they effervesced slowly, at the same time 
gelatinising. The sj)ecimens were weathered white to a consider- 
able depth. 
Analysis proved that the specimens were composed principally 
of lime, magnesia, silica, carbonic acid, and water, and that, not- 
withstanding their homogeneous 
appearance, 
they varied 
consider- 
ably in composition. 
Analysis 
numbers I. and II., each of which 
was repeated several times, represent the limits of this variation. 
I. 
II. 
Si0 2 . 
18-50 
SiO a 
• ® • 
22-03 
Fe 2 0 3 . • 
A1 2 0 3 . . . 
2-67 
4-63 
Fe. 2 0 3 ) 
ai,o 3 i 
. 
5-90 
CaO 
25-39 
CaO 
, . , 
24-01 
MgO . . . 
23-65 
MgO 
• • • 
19-53 
co 2 
10-95 
co 2 
. 
3-20 
H 2 0 
14-10 
h 2 o 
. 
25-23 
99-89 
99-90 
It will be observed that in 
No. I. the 
amount of 
water is 
much less and the amount of carbonic acid much greater than in 
No. II. The composition of the specimens was thus shown 
to be intermediate between that of dolomite and of a hydrated 
silicate of lime and magnesia, since, the carbonic acid being 
insufficient to combine even with all the lime, the remainder of 
the lime and the magnesia must have been combined with the 
silica. 
We were at once struck by the similarity between our specimens 
and certain serpentines occurring at Oxford, Canada (Zirkel, 
