HARDWICKE'S SCIENCE-GOSSIP. 



19c 



aqueduct by the north side of Craigmaddie 

 reservoir to the middle of Blairskaith Muir. Two 

 others run from the Clyde, at Raskielee, near 

 Erskine Park, diverging slightly as they go west- 

 ward. Another runs along the north side of the 

 railway tunnel west of Dumbarton. 



The district accessible from Glasgow is a perfect 

 blank, in so far as regards any record of the secon- 

 dary age. Scotland probably kept her head above 

 the water for most of the time, while Triassic 

 birds and Labyrinthodons, Liassic and Oolitic 

 Ammonites, the Plesiosaurus, and the teeming life 

 of the Chalk period flourished in English and con- 

 tinental seas. 



Stripped of the superficial deposits, Glasgow lies 

 immediately on palaeozoic rocks. The ancient 

 village doubtless owed its origin to the facilities 

 afforded by the lowest possible bridge over the 

 Clyde, admitting of a passage between the settled 

 districts of Carrick and Lennox. But the importance 

 of the modern city results directly from its geological 

 position in the midst of the coal-measures and car- 

 boniferous limestone. If Mauchline be considered in 

 the neighbourhood of Glasgow (and it is less than two 

 hours distant by rail), igneous and sedimentary rocks 

 of Permian age may be seen overlying the coal- 

 measures.* The Permian red sandstone of Mauch- 

 line is a notable building- stone. The great quarries 

 of Mauchline may be visited together with the 

 romantic scenery on the river Ayr at Ballochmyle. 



Returning to Glasgow, we find ourselves at the 

 western end of the great basiu of the coal-mea- 

 sures, which occupies a large portion of the counties 

 of Lanark and Linlithgow, and stretches northward 

 across the Pirth of Porth to the base of the Ochils 

 in Clackmannanshire. In spite of undulations of 

 the strata, and fracture by innumerable faults, this 

 great coal-field is fundamentally a long trough, 

 varying from six to fifteen miles in breadth, with an 

 axis running from S. W. to N. E. through Hamilton 

 and Grangemouth. The thickness of the coal- 

 measure strata here has been estimated by Mr. 

 James Geikief at 2,100 feet, with eighteen workable 

 coal-seams, amounting to from 40 to 70 feet in 

 aggregate thickness. But important as the coal- 

 seams are, Glasgow could never have reached its 

 present position except by the aid of the blackband 

 ironstones, so liberally scattered throughout the 

 coal- measures. A visit to the Govan Colliery, on 

 the south side of Glasgow, or to the ironstone 

 workings of Wishaw or Coatbridge, will amply 

 repay the visitor, whether his object be fossil- 

 collecting or the study of the processes by which 

 the mineral wealth of Glasgow is made available. 

 Where every quarry and every " blaes "-heap at 



* See Geological Survey, Sheet 14, Scotland (1-inch), and 

 explanation by Prof. Geikie. 

 t "Journal of the rron and Steel Institute," 18"2. 



every pit-mouth is eloquent with the story, it would 

 be useless to point out special localities for the 

 study of the physical geography and life of the 

 Coal period.* 



The millstone grit, underlying and consequently 

 coming to the surface in a belt surrounding the 

 coal-measures, presents few features of interest, 

 with the exception of the fireclays extensively 

 mined at Garnkirk. The series is, at least in the 

 neighbourhood of Glasgow, entirely wanting in the 

 boldly-marked subdivisions characteristic of the 

 millstone grit of England. 



The west end of Glasgow is built on the carboni- 

 ferous limestone series. This series, in Scotland, 

 is well known to differ vastly from the English 

 type, the uninterrupted marine conditions prevailing 

 in England during the period having given place to 

 repeated alternations of land and sea north of the 

 Scottish border. Hence, while in England the 

 whole period is represented by limestones, in Scot- 

 land only a few thin beds of limestone are inter- 

 calated among subaerial and purely sedimentary 

 beds. There is around Glasgow quite enough of 

 limestone for building and agricultural purposes ; 

 and besides, the coal and ironstone seams of carboni- 

 ferous limestone age are not far behind those of the 

 coal-measures in number and value. The top of the 

 series dips beneath the millstone grit, along a 

 crooked line, from Glasgow to [Kirkintilloch, while 

 its base is marked by the Campsie, Kilpatrick, and 

 Renfrewshire hills, and the Braes of Gleniffer and 

 Cathkin. Erom these trappean heights the carboni- 

 ferous limestone series is frequently separated by 

 faults ; but its true relations may be seen at Craigend 

 Muir, alongside of the turnpike road from Miln- 

 gavie to Strathblane;t at Douglas Muir, west of 

 Milngavie ; % at Elliston, near Howood ; § and else- 

 where. In these places the lowest beds of the series 

 rest on beds of porphyrites or melaphyres (old lavas), 

 or of volcanic ashes, which mark the last efforts of 

 an immense period of volcanic activity. 



Besides limestones, coals, and ironstones, the 

 Carboniferous limestone series near Glasgow 

 yields large quantities of sandstone for building 

 purposes, oil-shales, and alum. The latter impreg- 

 nates a shale between the main limestone of 

 Campsie and Hurlet, and its underlying coal. 

 Oil-shales are extensively worked at Linnwood, 

 near Johnstone. A great thickness of an 

 admirably pure and durable white sandstone 

 overlies the " Rough," or " Cowglen," or " Index" 

 limestone, and is ouarried extensively at Bishop- 

 briggs and Giffnock. The spacious galleries and 



* Sheet 23, Scotland (l-inch). of the Geological Survey 

 Map, contains in great detail the part of the Lanarkshire 

 coalfield to the south of Motherwell. 

 ' t Geological Survey (6-inch), Sheet 27, Stirling. 



% Ibid., Sheet 23, Dumbarton. 



§ Ibid., Sheet 11, Renfrew. 



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