LVI. Geological Notes and Queries:— Sections of Trap Rocks, etc., near Greenock

Abstract

The student of physical geology will derive much instruction in an afternoon’s ramble from Port-Glasgow to Kilmacolm, and from thence to Greenock, along the railway line in course of formation between it and Johnstone. Keeping the newer and most frequented road, along which the telegraph lines run, fine examples of porphyritic greenstone are exposed weathered completely white to the depth of half an inch. Near Kilmacolm, in the direction of Greenock, the line of railway has been cut through ordinary greenstone holding some zeolites and blue carbonate of copper. At the farm house, near this section, the greenstone changes into volcanic ash, in which lies one spur, not rich in metal, however, of the copper lode which extends from Lochwinnoch. The lode is here intersected by an oblique trap dyke, which throws it down on one side, while another dyke, fifteen feet in breadth, cuts through it vertically. Onwards towards the contractor’s offices, the rock varies to compact greenstone and varieties of ash, sometimes fantastically blended and enveloping large circular masses of hard trap (bombs), the ash sometimes vescicular, and the cavities filled with small brown crystals of carbonate of iron. Further on, the hard traps contain good examples of Thomsonite and calc spar, and above Port-Glasgow there is a fine exhibition of beautiful amygdaliod, of the same character (zeolitic and calcareous) as that near Johnstone and at the head of the Shaws waterfall at Greenock, but in better preservation. At the Greenock cemetery, a tunnel has been driven through This 250-word extract was created in the absence of an abstract