ON THE ERRATIC BLOCKS OF ENGLAND, WALES, AND IRELAND. 137 
On the local. blocks, which vary from large masses weighing 3 or 
4 tons, down to small pebbles, there are irregular scratches, but several 
of the erratics, which are scarce—probably constituting but ;1,th part of 
the coarser materials—have the striz finely and regularly marked along 
the longer axis of the stone in decided grooves. 
There do not appear to be any erratics on the neighbouring highlands, 
and the adjoining fields have not been worked so as to reveal sections. 
It is probable, however, that a much larger area than the one here 
detailed once existed, for a large felstone boulder was found in the Porter 
valley, near Hcclesall Road, Sheffield, a distance of 14 miles S.W. 
from Crosspool, and 600 feet lower in level, in composition and appear- 
ance identical with several of the Crosspool boulders. 
With the exception of the erratics catalogued, the large boulders 
consist either of millstone grit or coal-measure sandstones, which are 
local rocks ; the millstone grit series appearing only 1 mile to the west, 
while the grit series crops out in the Rivelin valley. 
Petrologically, however, many of these boulders differ from the rocks 
in the immediate neighbourhood, although they have evidently been 
derived from the same measures. 
Some of the gannister, e.g.,is compact, fine-grained and nearly white, 
but its identity is shown by a new fracture revealing traces of stigmaria. 
The following is a list of the principal erratics :— 
The specimens have been named by Professor Bonney. 
Although the size of some of the specimens is much less than that of 
those usually catalogued as boulders, yet their peculiarities render the 
list of value. 
1. A small well-rounded boulder, rather flat, fine scratches on all 
sides in the direction of the longer axis. Porphyritic tuff, 6 in. x 3 in. 
X2 in. : 
2. Roughly rectangular, smoothed angles little rounded. Felstone, 
1 ft. 2 in. x 9 in. x 9 in. 
3. Irregular shape, ends rounded. Quartz-felsite with hornblende, 
2 ft. 6 in. x2 in. x1 in.; 30 in. x 24 in. x 20 in. 
4. Subtriangular, rounded, and smoothed. Felstone, 7 in. x 7 in. 
x 6 in. 
5. Rounded ends, surfaces nearly flat. Felsite, 1 ft. 1 in. x 7 in. 
x4 in. 
6. Rhomboidal, with sharp angles and flat faces. Indurated tuff, 
8 in. x 4 in. x 4 in. 
hs Rounded, flattish oval. Tuff much decomposed, 6 in. x4 in. 
Xo in. 
8. Subangular, angles well rounded. Quartz-felsite with a little horn- 
blende, 7 in. x 4 in. x3 in. 
9. Rectangular, angles sharp. Grey magnesian limestone, 4 in. x 
3 in. X38 in. 
10. Subtriangular, rounded and smooth. Cherty magnesian lime, 
Vin. X 6 in. x 4 in. 
11. Long roughly triangular, ends rounded, much decomposed. 
Felstone, 1 ft. x 4 in. x 4 in. 
12. Roughly rectangular, somewhat rounded at one end. Felstone 
and vein stuif, 2 ft.x1 ft.x10 in. 
a Rounded oval boulder, smoothed. Quartz-felsite. 8 in.x5 in. 
Xo in. 
