The Plymouth reef consists of a middle part a thousand yards long, and lying directly across the entrance of the Sound, and of two wings bending inwards at a small angle, each 350 yards long, making in all 1700 yards, or very nearly a mile. Advantage having been taken of a shoal, the depth under low water averages about 36 feet, and the height above low water is just 20 feet. The slope towards the sea forms an angle of 22° with the horizon, giving an increase of breadth of nearly two feet and a half for each foot of descent; the slope towards the land forms an angle of 33° with the horizon, and increases one foot and a half for each foot of descent: consequently the increase of breadth on the whole is four feet for one of descent. The whole mass is composed of stones blown by the force of gunpowder from limestone rocks on the river side, from whence they are rolled at once on board barges, which sail to the spot and drop them into sea. The whole weight of the reef is estimated at 2,500,000 tons. It may be curious to compare it with the largest building in the world. The Great Pyramid of Egypt measures 687 feet on each of its four sides, and the perpendicular height is 480 feet; these dimensions, supposing the Pyramid to be solid, give a content of 76,500,000 cubic feet, and a weight exceeding 5,500,000 tons, more than double the weight of the reef, and the materials are large blocks hewn into regular forms, transported from a considerable distance by land carriage, then raised into the air, and finally laid with cement in their exact places. The artificial reef has cost a million of money; the Pyramid must have required an amount of labour represented at present by perhaps twenty times that sum, a building without use or beauty, while the reef has made Plymouth one of the best harbours in the whole world. Maker measures 1867 statute acres. If the artificial arrangement were attended to, 967 acres must be deducted. Annual value of the Real Property as £. _s._ _d._ returned to Parliament in 1815, including the part returned as in Devonshire under the name of Vaultershome 3465 0 0 Poor Rate in 1831 821 16 0 Population, in 1801, in 1811, in 1821, in 1831, Cornwall 1691 3678 1796 1545 Devon 1614 1569 1222 1092 ―――― ―――― ―――― ―――― 3305 5247 3018 2637 The fluctuations in the number of people are evidently caused by the difference of war and peace, in a parish so much blended with the great naval and military establishments of Plymouth. Present Vicar, the Rev. Daniel Stephens, presented by the Lord Chancellor in 1796. GEOLOGY.