18 Me. J. Brtce on the Discovery 



applied to the great chimney of the works of Messrs. Tennant and 

 Company at St. RoUox, near Glasgow, which was erected frona the 

 designs of Messrs. Gordon and Hill, and is, with the exception of the 

 spire of Strasbourg, the Great Pyramid, and the spire of St. Stephen's 

 at Vienna, the most lofty building in the world, being 436 feet high 

 above the ground, and 450 feet high above the foundation ; and it has 

 been found that the stability of that chimney is suited exactly to the 

 maximum pressm'e of wind ah-eady mentioned, of 55 lbs. per square 

 foot. 



March 19, 185(3. — The Peesident in the Chair. 



Dr. Decimus Hodgson was elected a member. 



Mr. Bryce described some recent Observations on the Granite of the 

 Island of Arran. 



Notice of the Discovery of a New Granite Tract in Arran. 

 By JAiiLES Bjixci:, M.A., F.G.S. 



The northern and southern halves of this celebrated island are 

 remarkably distinct in their physical featm-es and geological structure. 

 The former, bounded southwards by a line running almost due east and 

 west from Brodick bay to lorsa water-foot, consists of a mass of 

 peaked and rugged mountains, intersected by deep and wild glens, which 

 diverge from a centre, and open seaward on a narrow belt of low land. 

 The southern half consists of a rolling table-land, bleak and uupic- 

 turesque inland, but breaking rapidly down seaward into a coast border 

 of great romantic beauty. The general elevation of this portion is 

 from 500 to 800 feet ; and the irregular ridges which traverse it, most 

 usually in a direction nearly east and west, do not rise above 1,100 or 

 1,400 feet. The northern portion, on the other hand, rises into moun- 

 tains passing 2,000 feet, and culminates in the south summit of Goatfell, 

 having an altitude of 2,875 feet, while many of the peaks reach a height 

 very little less. The rocks constituting this mountain group are granite 

 and the old slates ; the latter flanked on the north and east by sand- 

 stones and limestones of Devonian and carboniferous age. The entire 

 southern plateau is composed of sandstone, broken through and overlaid 

 by vai'ious trap rocks, chiefly greenstone and porphyry. The whole of 

 this sandstone we refer to the age of the coal formation, on the ground 

 that limestone, with true carboniferous fossils, occm's in repeated alter- 

 nation with it, and that there is an entii-e absence of fossils of New-Eed 

 types ; we cannot see that there is any evidence for separating a por- 



