Geological Society. 529 



which ranges through the city. On the other side of the Clyde they 

 reach as far as Mr. Dixon's iron-works, but further down the river 

 their thickness is not great. At Mr. Smith's property of Whiteinch 

 twelve feet of sand overlie thirty of soft clay and sand. 



The bed containing recent shells at the entrance of the Arkleston 

 Tunnel*, near Paisley, is 80 feet above high-water level ; and a simi- 

 lar bed at Port Glasgow is 40 feet. In both instances it is overlaid 

 by laminated sands similar to those at Toll Cross, and on which the 

 greater part of the city is built. Their highest level in Glasgow is 

 about the same as that at Arkleston. 



The boulders are found almost throughout the basin of the Clyde 

 where denudation has not taken place subsequent to their deposition, 

 except in the elevated trap districts, where they are very rare ; the 

 only instances mentioned in the paper are the Baker's Reservoir on 

 the summit of the trap range of Kilpatrick, and Cochney Loch ; nor 

 do they appear on those strata which have been upheaved by trap. 

 On the side of the road near Cartlane Bridge is an accumulation of 

 very large primary and transition boulders without till, forming a 

 kind of escarpment on the brow of a very precipitous bank leading to 

 the valley of the Tee. The opposite slope is crowned with beds of 

 sand. The level of these beds is stated to be 550 feet above the sea. 



Near the source of the Avon is a deposit of sand and gravel 50 feet 

 thick ; and similar beds occur at Greenock Mains, on the Ayr road 

 from Muirk Kirk, ,West of these deposits, on White Haugh Water, 

 are enormous beds of till. Boulders or fragments of compact flesh- 

 coloured felspar and reddish porphyries are very rare in this district, 

 but are common in the higher parts of Lanark and Ayr, where these 

 rocks form dykes"or beds in old red sandstone. Mr. Craig has never 

 found the slightest trace of the coal-measures north of the trap which 

 forms its northern boundary, 



The following is a summary of the author's observations respect- 

 ing the nature of the boulders at Bell's Park, and the extent to which 

 they have been scratched : — 



Greywacke, similar to that which is associated with slate near Rose 

 Neath, and mica-schist above Lass on the borders of Loch Lomond. 

 Blocks very abundant, generally smooth, angles rounded, scratches 

 longitudinal, seldom or never crossing each other. 



Porphyritic traps and basalts are next in abundance ; a few of the 

 basalt-blocks are scratched, but none of the porphyritic. 



Granite. — The felspar large-grained ; masses few in number, much 

 rounded, very smooth, not scratched. 



Old red sandstone and conglomerate. — Abundant, much rounded, 

 never scratched. The conglomerate blocks are very like a variety 

 near Glen Sannox in Arran. 



Quartzose rock. — Blocks not abundant, very smooth ; more rounded 

 than any other, not scratched. 



Coal sandstone. — Blocks angular, scratched longitudinally. Frag- 

 ments of iron-stone rare and angular, but smooth. 



* At this tunnel a bed of coal is stated to have been changed by trap into 

 a bed of pyrites ; but a stratum of limestone, though only two feet from 

 the trap, is reported to retain its organic remains. 



