286 Scientific Intelligence. 
On the origin of some Magnesian and Aluminous Rocks ; by T. 
diectioe Hunt, F.R.S., of the Geological Survey of Canada. (From the 
Canadian Naturalist for June, 1860. —In common with other observers, 
nesia and oxyd of iron are deposited during the evaporation of many 
the waters of the Ottawa river. I have also suggested that the silicates 
thus produced may have contributed in a considerable degree to the 
formation of rocks. (This Journal, March, 1860, p. 284). A hydrous 
sili of magnesia which approaches in composition to MgO Si0%, 
meses and bite forms extensive beds wit Poems and age in 
group, and in the lacustrine series known as the St. Ouen limestone, where 
it forms very fissile shaly layers, enclosing nodules of _ je 
The — = nie sepiolite, which I have ae and described 
and m 
ignition is soluble in acids, which a is not. We cannot however — 
serpentine may hav Se formed from the alteration of a mixture 
of sepiolite and carbonate of magnesia. In chlorite, which often he 
o-m ; 
amount of ferrous oxyd which in part replaces the latter) in sar 
as 6:3: 5, while in a 
1:1, and in most argillaceous sediments the proportion o 
er. It is evident, therefore, that chlorite could not be for 
mixture of sepiolite with clay, or st with pure alumina, wit 
elimination of a large amount of silica, and we are led to to regard i aiid 
having been generated by the cece iaiat a silicate of alumina oF a 
with magnesia, which was probably present in the unaltered sedi 
in the form of. carbonate. Unless indeed the process, which according 
to Scheerer, has in recent times caused the deposition from waters, of 
5 
Seer 7 oe ean a eceepa 
oe 
