On the Bituminous Shales of Linlithgowshire^ &c. 23 
cano. The Leaven Seat limestone is found immediately above 
these beds; and as it abounds in marine fossils, another 
change of land and sea must have ensued at its formation. 
The whole strata were once more elevated by the great fault 
forming the boundary of the Torbanehill mineral basin. 
And if the Craigs and Shotts Hills were of contemporaneous 
age with the Bathgate range, we may easily trace the shores 
of the lake in which this very peculiar mineral substance 
was formed ; and we will likewise be led to the conclusion 
that it was separated by physical barriers from the upper 
Coal Measures of the Clyde Basin. The contemporaneous 
character of the traps found to the eastward of the range, 
both in Edinburgh and Linlithgowshire, has been ably 
proved by the labours of Mr Geikie and others. 
It is surely in nowise very hypothetical to assume, that 
some relation exists betwixt the intense diffusion of trap, 
and the extensive prevalence of bitumen in the district. 
Bitumen oozes from the trap rocks of Winchburgh ; it occurs 
in circular blots in the Binny sandstone, and permeates the 
overlying limestone shales of Mid-Calder and Broxburn. 
Now, we know of two methods by which this substance is 
eliminated in nature. First^ It appears when we confine 
organic matter in a close vessel, and when in the absence 
of the oxygen of the atmosphere, the carbon and hydrogen 
unite to form its various compounds. Secondly, It is ejected 
as an oily fluid from mud volcanos. Mr G. Walls, in an 
able paper on the geology of Trinidad, remarks : — " The phe- 
nomena of salses, or mud volcanos, consisting of the solution 
of inflammable gas, accompanied by the discharge of a muddy 
fluid and asphaltic oil, is perhaps closely related to the activity 
first described, as carburetted hydrogen may be disengaged 
in the direct formation of asphalt. Several of them occur in 
Trinidad, also in the newer Parian formation/'* I am in- 
clined to ascribe the bitumen of the Balbairdie household 
and gas coals, — and in bituminous coals generally, — to the 
first method of forming bitumen. Again, I think that the 
structural character of the district fairly justifies our ascrib- 
*■ Geological Journal, vol. xvi., 1860. 
