46 
THE GEOLOGIST. 
another condition under which bitumen w as eliminated. In this case 
it is the result not of mechanical deposition, but of subsequent chemi- 
cal action from decaying organic substances. Again, the action of 
the currents was resumed, and fresh bituminous shales were formed. 
When the contemporaneous traps on the north-west side of our 
section were ejected, the same succession of physical changes con- 
tinued. Bitumen occurs in globules both in the contemporaneous 
traps and in the limestones. The limestones indicate three marked 
alterations in the level of the land. Eirst, the Kirkton limestone, 
with its leafy laminae, and curiously baked beds of cherty porcelain, its 
interstratified ash, and over-capping basalt indicate proximate vol- 
canic activity when forming. Fluvio-marine fossils are found in it. 
The land then sank so far as to allow the building corals to com- 
mence their labours ; a reef was now formed which was added to by 
shells dashed in by the surf from the neighbouring sea, and the pre- 
cipitation of carbonate of lime from a sea surcharged from its prox- 
imity to a volcanic cone ; thus the great belt of the limestone of the 
hills was formed. But immediately after the land was subject to as 
rapid an elevation ; as is manifest from the Stigmarias found in the 
upper bed of the limestone, — the lower beds abounding in deep-sea 
shells. Ash-beds also cover it. The hills now seem gradually to 
have risen above the waves, and a prevalence of freshwater strata 
filled the small Torbane Hill basin. But all this time the volcano did 
not stop its activity, as is evidenced by the thick ridges of inter- 
bedded basalt whicii may be traced terracing the country upwards 
from Bathgate. It is easy to suppose that sheets of bitumen, as at 
the prior period of the Binny sandstone, floated on the waters of this 
lagoon ; that in one time in particular, a very large quantity was 
given out, and thus, aided mayhap by ejections Irom beneath, the Tor- 
bane Hill bed was formed. May not the round circular masses in the 
Torbane Hill mineral, which so puzzle microscopists, be the result of 
the action of currents, — only, however, on a smaller scale than those 
visible to the naked eye in the other rocks of the district ? In sug- 
gesting this hypothesis we make allowance for the fact that at other 
t'mes the basin was elevated so that morasses could accumulate, and 
thus the beds of coal be formed. The district thus exhibits evidence 
of both modes of the elimination of bitumen. 
In the upland country west of the Torbane Hill basin there is a sin- 
gular absence of trappean ridges. The district rises into a series of 
undulating hills formed solely of the upper members of the carboni- 
ferous system of Lanarkshire. The lower carboniferous volcano had 
ceased previous to their deposition ; and the Bathgate hills probably 
formed elevated land at the base of the great strait in which these 
strata were depositing. Slowly the laud rose and fell, morass after 
morass accumulated to be compressed into future coal-beds after being 
covered over by sand and mud. Bitumen was thus formed through 
chemical agencies. Its source is manifest from the microscopic struc- 
ture of the coal, which is entirely of woody origin, not exhibiting 
traces of clay or sand from drift. The beds of this upper formation 
