Chap. VIII.
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The stone which Smeaton selected from the Isle of Portland was obtained where it layin beds nearly parallel with the surface of the land, and is covered with a small quantityof earth.
There are several beds, varying in thickness from 2 to 4 feet and upwards: these arecovered with a stratum called a cap, which is formed of shells of various kinds ; sonic ofthem, as the Cornua Ammonis, are upwards of two feet in diameter; this capping is veryhard, and is usually detached by blasting with gunpowder.
After this cap has been removed, the quarry-men proceed to cross-cut the large flats,which are laid bare with wedges, and split off* the Portland , not in a very even manner,but in masses, the quarry-men, with a tool called a kevel, which is at one end a hammerand at the other an axe, whose edge is short and narrow, like a pick, reduce it to somethinglike a cube, or regular shape. The face of the kevel is not at the hammer end quite flat,but a little hollowed out, which gives rather a sharp edge to two of its opposite sides,which are parallel to the handle ; and by this means it is made to bite more keenly uponthe stone, and to bring off a spawl or large shivers. 'Hie edge at the pick end is abouthalf an inch in breadth.
Dartmouth Harbour is not only beautifully situated, but very safe for vessels, andcapacious enough to hold 500 sail. It is defended by a fort, situated where the ancientcastle stood.
The Dart is navigable to Totness, where arc numerous manufactories.
Exmouth., at the mouth of the Exe, is situated near the shore, where the cliffs open as itwere to receive it. It is sheltered from the north-east and south-east winds by lofty hills;this was the birth-place of Sir Walter ltaleigh, who was the author of the History of theWorld, as well as its greatest navigator.
Sidmouth was formerly a good sea-port, where the small river Sid flows toward the oceanand loses itself among the pebbles on the beach, in consequence of the alluvium with whichthe harbour is almost choked up.
Axmouth , on the river of that name, is another small port, monthly resorted to by fishermen.
Lyme lieyis , situated on the river Lyme , near the west bay, in a cavity between tworocky hills, has a spacious quay, and round the harbour are several forts for its defence ;the chief is called the Cobb, which is very ancient, and composed of fragments of rock, inhuge masses piled together ; this fabric is of the greatest importance on this coast, as thereis between Start Point and the Portland Road no other shelter for shipping. The Cobb,distant about \ mile from the town, is in the shape of a half moon, with a bar in themiddle of the concave part. The stones are not cut or bedded in cement, and the surgeplays in and out through the interstices. When a reparation is requisite, the new stoneobtained on the coast, of as large a size as possible, is floated by means of casks chainedtogether, with a man mounted on one to steer them. Such is the description given byLord Keeper Guildford in his time, and reported in North’s life of that nobleman.
This is a very early example of a breakwater formed with pierre perdu.
Weymouth is situated within a fine bay, admirably protected by lofty hills on all sides.Leland observes, “ that the tounlet of Waymouth, lyeth strait agayn Milton (Melcombe)on the other side of the haven, and at this place the haven is but a small brede; and thetrajectus is by a bote, or a rope bent over the haven, so that in the ferry bote they use nooars." lie mentions also, that there is “a trajectus into Portland , by a long causey ofpebble and sand.”
Poo/e, on the north side of the bay, stands on a peninsula, connected by a narrow isthmuswith the main land, which is J mile long, and } 2 mile in breadth. This is surrounded by aspacious quay.
At the east end of the bay, about 3 miles north-west of Studland, is the Isle of Brownsea,
in length, and ^ in breadth.
Christchurch Harbour , Hampshire, is situated at the bottom of a deep bay, lying betweenthe Isles of Wight and Purbeck, and at the mouths of the Avon and Stour. These riversform in their passage to the sea an inland basin, which is defended from all winds ; informer times the mouth of this harbour was much more extensive, as the heads of landwhich bounded it, being formed of loose sand and iron-stone, have been, to a very con-siderable extent, washed away; much of this sand now forms a range of hommacks or sandhills, extending from Christchurch Head north-eastward, to the south point that now con-stitutes the harbour’s mouth ; here a bank has been thrown up, which separates the basinof Christchurch from the sea; the sands have thus driven the mouth of the river to thenorth-east.
The two rivers, which drain a considerable track of country in time of floods, pour downa quantity of water and keep the channel open, hut in consequence of the small rise of thetides, which is not more than from 5 to 7 feet spring tides, and from 4 to 6 at neaps, it isnot very practicable to obtain a very great depth of water in the harbour, and the increaseof the sands, their constant motion, and the flatness of the bottom of the bay, also contributeto prevent anv great improvement being carried out.
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