188 Professor SepGwick on the 
4. The upper dyke in Eglestone Burn, and the dyke in Lune- 
dale, must have originated in a cause of the same kind with that 
which produced the dyke last-mentioned. 
5. The dyke in Lunedale, is probably connected with the 
protruding masses of trap near Saddle-bow, (See Pl. vin. Fig. 3.) 
and these protruding masses cannot possibly have been formed 
by infiltration after the deposition of the other strata; from which it 
follows, that the dyke in Lunedale was probably injected from 
below. I may add, that there is no fact which makes the con- 
trary opinion in any way probable. 
6. It would be highly unphilosophical, to class these dykes 
and masses of trap among igneous rocks, and at the same time, 
to class the beds, and tabular masses of trap in the higher part 
of the dale (the Whin-Sill) among aqueous deposits. 
7. The beds and tabular masses of trap, have produced 
mechanical effects which it is impossible to account for, on the 
supposition, that the strata originated in a succession of aqueous 
deposits. 
8. These tabular masses have produced, in the texture of 
the neighbouring rocks, many important changes which cannot 
be explained by any hypothesis, which rejects their igneous 
origin. On the contrary, many of the changes may be imitated, 
by direct experiment, and almost all of them may be explained 
on the hypothesis which admits the igneous origin of the trap, 
and supposes it to have acted, both chemically and mechanically, 
on pre-existing strata. 
The observations on which these conclusions are founded, 
have been given with sufficient detail, and various illustrative 
specimens have been brought from the different localities, which 
the Members of the Society may have an opportunity of examining 
in the cabinets of the Woodwardian Museum. 
a a 
