THE NEW BREAKWATER AT PORTLAND.

Hawke's Bay Times, Volume II, Issue 28, 9 January 1862, Page 6 (Supplement)

THE NEW BREAKWATER AT PORTLAND.

Tho Times contains a description of the new breakwater, just finished, at Portland :—“ The breakwater was first suggested in 1791, but it was not until half a century afterwards (hat the work was actually taken in hand. In the year 18-14 the construction of this enormous barrier was formally recommended ; in 1817 an Act of Parliament provided for the execution of the scheme ; in 1819 the first stone was laid ; and now, in 1861, we announce the substantial completion of the enterprise. Portland harbour is now effectually protected against.the fury of the elements, and it remains only to fortify it against the attack of an enemy. The description given of the work and of the process employed is very remarkable. In one sense nothing could be simpler : in another nothing moi-e difficult. A breakwater is nothing but a wall built in the sea, resting on the bottom, and rising above the waves. This wall, moreover, builds itself—that is to say, the stones of which it is composed shake themselves into their places, settle themselves by their weight, and remain fixed and compact from the operation of the same cause. Nothing more, therefore, is required than to pitch a sufficient number of stones into the sea at the right place. So far the work seems even easier than that of building the dry walls which servo for hedges in our northern counties ; but the difficulties soon begin. In tho first place, the wall which has to withstand the shock of the waves at their very highest, is necessarily of enormous thickness. No land wall, however strong, can give any idea of the dimensions of walls built beneath the sen. A hole bored through tho Port-

land wall would represent a tunnel nearly 100 yards long, for the base of this breakwater is actually 300 feet wide. The height of the wall, again, is 100 feet, and its length upwards of a mile and a half. On land such a pile would look like a little mountain ridge, and would form indefid,- quite a respectable chain of hills in some of our flat -countries. Still, as the stone in this was closemthkhd In quantity abundant enough even for such -’a tfork the difficulty may be thought not. very - Sferiods. But how were these stones to bo carried to thfi sea and dropped into it ? Close to the shore ifmay be all very easy ; but how when the material has to be carried out for half a mile or a mile, aS the work extends ? That is the part of the process which taxes the engineer. As the stone is quarried from a height, above the sea level, it will run down a tramway by its own weight, and can be readily turned into the sea at any given point ; but how is the tramway itself to be made ? The report which we published on the 11th will have shown that this was the great difficulty to be overcome. Given a good tramway, and the rest was easy. The convicts dug the stone and the loaded waggons ran smoothly along the inclined plane, and when they came to the end of their course were made to ‘ topple’ over their cargoes into the sea. The one difficulty was the tramway itself, which w r as neither more nor less than a railway built on piles and running out to sea like a pier. Building it w'as like building a huge scaffolding under water. The timbers were required to be of an immense strength, and waterproof besides, and the tramway had to grow as the breakwater grew yard for yard. All this, however, has been accomplished, and five million tons of stone have been dropped scientifically into the sea. The result is a great artificial reef projecting many feet above the water, and effectually securing the harbour against the onset of the waves. Hitherto we have been only fighting against nature, but we are now preparing to contend with man. At one extremity of this breakwater will stand a fort of the most remarkable character. It will be at once the strongest and most powerful fort of its kind in the country. That much is decided ; but it is scarcely possible to decide more, for the simple reason that nobody can tell what new discoveries in the science of attack and defence a few' years or a few- months may bring about. Up to a certain height above the sea the fort will be of granite ; and all but entirely solid. Above this it may be all granite still, or granite with iron facings, or all iron. Similarly, as regards the armament, it is arranged that the fort shall mount 6(1 guns, and that these guns shall be the heaviest and most pow'erful known ; but wdiether they will be 100-pounders or 500-pounders depends upon the development which Sir W. Armstrong and his colleagues may by that time have given to the manufacture of artillery. Two classes of inventors are now running a race against each other. Our ironmasters are forging impenetrable plates, and their rivals arc devising irresistable guns. Nobody can say which will win, but the great fort at Portland will represent and exemplify the resources of both alike. We observed that the expense of the Portland breakwater has been comparatively moderate. It has cost less than a million of money, which is within the latest estimate, and all the most expensive work is now done.”