20 Proceedings of the Royal Physical Society. 
with coal-seams ; and, thirdly^ the coal strata proper, which 
some hold contemporaneous with the English Coal Measures. 
In some places the marine limestones are 70 or 80 feet thick, 
but generally their thickness only averages a few feet. 
In some districts the first group of strata is absent, and 
the marine limestone rests on the Upper Old Eed Sandstone 
beds. The first two groups contain all the bituminous shales 
we are about to describe. 
The Leaven Seat Shale. — One of the uppermost of the 
marine beds has for several years been wwked at Leaven 
Seat, near Longridge. It is capped by a thick bed of shale, 
a foot and a-half of which yields, on distillation, so much 
paraffin as to render it of commercial value. The limestone 
has been traced throughout the uplands of Lanarkshire into 
Eenfrewshire, and this bituminous shale has been found 
richly developed above it in various parts of its course, 
particularly we believe near Castlecary. 
There are two interesting mineralogical characteristics 
of this shale. In many places its passage from the sub- 
jacent limestone may be traced. At its junction with the 
limestone, it has most of the petralogical characters of the 
latter rock ; but as the bed thickens it gradually assumes a 
clay base. The same features are likewise distinctive of 
the shale below this in geological position, about to be de- 
scribed. The prevalence of fish scales in the shale itself, 
as well as the abundance of shells and corals in the lime- 
stone immediately below it, indicate that it probably owes 
its bituminous character to an animal origin. 
Mid-Calder Shale. — The area of the series we have enu- 
merated as the lowest member of the Scottish group, extends 
in segmental fashion from the Bathgate Hills to Fifeshire, 
and thence across the Forth at Kirkcaldy, to Qilmerton and 
Carlops. A well-known fresh-water limestone, extensively 
worked at Burdiehouse, is know^n to extend throughout this 
area. A shale capping this limestone is in some parts of 
Linlithgowshire so richly bituminous as to have been mined 
for the purposes of distillation. Chemical works, with this 
view, have been erected at Mid-Calder and Broxburn ; and a 
careful observation of this shale in other quarters shows that 
