Among the principal sea-ports of the United Empire, Greenock is justly entitled to a distinguished place. Although of comparatively modern date, it has left many of its ancient predecessors and modern rivals in the background, and at this moment continues to advance rapidly in commercial enterprise and prosperity. The recent formation of quays and docks of corresponding dimensions, affords to this harbour every facility for vessels of heavy burthen. The town possesses several handsome buildings, the principal of which are the church, the Tontine, or great hotel, and the CUSTOM-HOUSE. Of the latter, with the immediate scene of commercial activity and forest of masts by which it is surrounded, the engraving opposite presents a vivid and faithful representation. It is a structure of great elegance, and, as an illustration of the chastest style of Grecian architecture, it would be difficult to point out a finer specimen either at home or abroad. The quality of the materials too is every way worthy of so fine a monument of national prosperity; and a fair estimate may be formed of the superiority of the workmanship, when we state that a sum of not less than twenty thousand pounds was expended in its erection; a fact which evinces at the same time the high importance attached to Greenock as a depot of the national revenue. The river Clyde is here about three miles broad; but, as also at Port-Glasgow, the navigable channel is little more than three hundred yards across. The bay is formed by an expansion of the Clyde, into which several bold points of land project from the northern bank, over which the mountains of Argyll, gradually receding till their summits are lost in the sky, present a landscape of almost Alpine beauty and magnificence.