44 



THE GEOLOGIST. 



Axis. 



W.NN. 



Upper Lanarkshire coal measures : — 



Wholly fluviatile organic characters. 



Beds of marine and fluvio-marine lime- 

 stone intercalated with shale, coal, 

 ironstone, and stratified trap. 



Shales, sandstones. 



3. Sandstones, shale, and a bed of coal. 

 2. Freshwater limestone. 



1. Shale, sandstone, tufa. 



On the Bathgate Hills the marine limestone is sixty feet thick, 

 and the fluviatile limestone about twenty feet thick. But towards 

 the south-west, on the borders of Edinburgh and Lanarkshires, the 

 marine limestone thins into beds of from three to six feet thick, 

 whilst the freshwater bed is above fifty feet thick. 



The Torbane Hill bed lies in number two of the left-hand series 

 of strata. Along with two or three local coal-seams, it occupies a 

 small mineral basin some two or three miles in area, lying immedi- 

 ately above the mountain-limestone, but stratigraphically distinct 

 from the upper Lanarkshire coal-measures. The petrological struc- 

 ture of the surrounding strata is very unique ; let us try to evolve 

 their Pii story. 



The physical changes closing the life-era of the Scott'sh old red 

 sandstone system are difiicult to determine. From various geolo- 

 gical reasons, the chief of which are the wave-ripples on the sand- 

 stones, and the physical structure of the surrounding mountain-chains, 

 it has been deduced that central Scotland was a strait or frith bounded 

 as now by the prominent peaks of the northern and southern High- 

 lands. Islets, covered by a strange vegetation, dotted tins Matery ex- 

 panse ; from the eastward strong currents brought down the spoils of 

 a now lost land, depositing the shales and sandstones so predominant 

 round the Scottish metropolis. In this quarter, too, an intense vol- 

 canic activity prevailed. 



The trappean bosses, which form so prominent a feature in the 

 landscape round Edinburgh, were mostly erupted at this time. So, 

 at least, the labours of Mr. Geikie and others go to prove. 



Erom St. Abb's Head to Bathgate a chain of volcauos sent up their 

 lurid contents into the Carboniferous sky. Xowhere was this activity 

 more intense thui on the Bathgate hills. The freshwater series to 

 the eastwards of our section are everywhere intercalated with trap ; 

 some of it dev(^loped as aerial ash-beds, the rest as submarine green- 

 stones. The prominences round AYinchburgh, Binny, and Linlithgow, 

 which the railway-traveller may remember so boldly characterize the 

 scenery, are the memorials of these eruptions. The spot pointed out 

 as the axis of the hills was undoubtedly the vent of a very active vol- 

 cano. Immediately above Bathgate four or five great beds of basaltic 

 greenstone and ash lie so intercalated with the aqueous strata as to 



