356 Coal Formation of Nova Scotia. 
9. There must have been repeated sinkings of the dry land to 
allow of the growth of more than ten forests of fossil trees one 
above the other, an inference which is borne out by the indepen- 
dent evidence afforded by the Stigmaria found in the under-clays 
beneath coal-seams in Nova Scotia, as first noticed in South Wales 
by Mr. Logan. ro 
3. The correspondence in general characters of the erect trees 
of Nova Scotia with those found near Manchester, leads to the 
opinion that this tribe of plants may have been enabled by the 
strength of its large roots to withstand the power of waves and 
currents much more effectually than the Lepidodendra and Sigil- 
lari, which are more rarely found to retain a perpendicular po- 
sition. ~ naga es, - 3 
_ Lastly, it has been objected that if seams of pure coal were 
formed on the ground where the vegetables grew, they would 
not bear so precise a resemblance to ordinary subaqueous strata, 
but ought to undulate like the present surface of the dry land. 
In answer to-this Mr. Lyell points.to what were undoubtedly ter- 
restrial surfaces at the South Joggins, now represented. by coal- 
seams or layers of shale supporting erect trees, and yet these sur 
faces conform as correctly to the general planes of stratification 
as those of any other strata. Seee~ Hae 
_ He also shows that. such an absence of superficial inequalities 
and such a parallelism of successive surfaces of dry land, ought 
to be expected according to the theory of repeated subsidence, 
because sedimentary deposition would’ continually exert its lev- 
elling action on the district submerged. what baer 
Arr. XII.—On the Coal Formation of Nova Scotia, and on the 
Age and Relative Position of the Gypsum and accompanying 
© Marine Limestones ; by C. Lretx, Esq. F. G. 8. &e. &¢- i 
[Communicated to this Tougnal by the author.) a 
_ Tum stratified rocks of Nova Scotia more ancient than the car 
boniferous consist chiefly of metamorphic clay-slate and quartzite, 
their strike being nearly east and west. Towards their northern 
— Jimits these strata become less crystalline and contain fo ils, 
some of which Mr. Lyell identifies with species of the upper Silu- 
rian group, or with the Hamilton group of the New York geol 
gists. : 
