142 DAVIS: SOURCE OF BOULDERS IN CALDER VALLEY. 
wells have been dug to a depth of twenty-eight and thirty- 
feet, and at Thornhill and Dewsbury excavations have proved 
the deposits to be between forty and fifty feet in depth. 
Still further up the valley, from Elland to Sowerby Bridge, 
the gravels and boulders occur in some force, and are at 
least twelve to sixteen feet deep. The valley nearer its 
source than the latter locality is almost devoid of gravels ; 
and where they do occur, as at Mytholmroyd, the travelled 
boulders are rare, or altogether absent. From Sowerby 
Bridge southwards the drift or gravel is composed of rounded 
pebbles and sand ; these, near the surface, are almost entirely 
derived from the local sandstones and calliards ; in the lower 
strata boulders of granite, trap, and syenite become gradually 
more frequent, until in the lowest parts they attain a great 
preponderance, and rocks of local origin are almost as rarely 
found as crystalline ones were in the upper part of the 
series. In the sections low down the valley, the boulders 
are frequently of considerable size, and at Dewsbury masses 
of granite and limestone were found near the base of the 
section exceeding a foot in diameter ; they were in all cases 
well rounded and quite devoid of scratches. The following 
section of a well sunk at Dewsbury may be taken as an 
average example : — 
1. Earth and sandy subsoil 7ft. 6in. 
2. Boulders, consisting in the upper part of sand- 
stone with, a slight intermixture of granite, 
etc., gradually merging into 24ft. Oin. 
3. Boulders, almost entirely of crystalline rocks 
not occurring in the district in situ 6ft. Oin. 
4. Clay with sand and boulders 5ft. Oin. 
Carboniferous sandstone 
A remarkable circumstance is the occurrence in the lower 
beds of rounded masses of flint, along with granite, 
syenite, and trap rocks, the latter having been identified 
with their parent rocks in Westmoreland and Cumberland, 
