SPITHEAD FORTS. The troubled state of European politics which gave rise in 1859 to the volunteer movement, led also the recommendation of an extensive plan of defenses for the arsenals and coast. A board of commissioners drew up a scheme for these defenses, to cost about £5,000.000, of which a sum of £2,000,000 was for Portsmouth. Spithead, and the neighboring coast. At present the entrance to the important arsenal and dockyard at Portsmouth is defended by fort Monckton on the Gosport side, Southsea Castle on the opposite side, Cumberland fort at the entrance to Langston harbor, Lumps and Eastney forts between the two last named, and some defensive lines between the island of Portsea and the mainland. £580,000 was voted in 1860 as a beginning, to increase the number and strength of these forts, to build detached forts on shoals in the sea between the mainland and the isle of Wight, and to raise fortified lines on Ports down Hill (the principal work being fort Southwick), wholly northward of Portsmouth harbor. The works were commenced, but the often-conflicting lessons furnished by the American war led to much delay and endless variations of plan.
The national defense commissioners had proposed five advanced forts on the shoals known as Horse Sand, Noman or No Nau's Land shoal, Sturbridge shoal, Spit point, and a point intervening between Horse Sand and Portsea island. But after much dis cussion and numerous alterations of plan, it was only in 1864 that it was determined to proceed with the foundations at least of two—the Horse and the Noman forts. The foundation of each fort consists of rings of stone-work, laid on the levelled bed of the shoal, tapering a little upward from a width of 54 ft. to one of 43 ft., the outer diam eter of the ring gradually lessening from 231 to 213 feet. From 20 to 15 ft. of submarine
masonry is required. Outside the rings of stone are layers of rubble to protect the stone-work from the action of tidal rush. Two years later similar forts were begun on Spit bank and St. Helens shoal. In 1865 a mortar-battery had been erected at Puckpool in the isle of Wight, commanding at long range the approach to Spithead. In 1868, after it had been found impossible to secure a foundation for a fifth fort on the Stur bridge shoal, Puckpocl battery was strengthened and armed with 30 mortars and 4 25 ton guns.
All this time the government had not determined which of three modes to adopt for constructing the forts—whether to form them entirely of iron, or of granite faced with iron, or simply of granite, the facing for after-consideration. The plan most in favor with tha government in 1866 was to erect on each of the foundations at Spithead a revolving iron fort or tower of enormous magnitude.
Circumstances in 1867 induced the government again to pause. Experiments on the Rodman 15-in. and 20-in. guns led some engineers to believe that no iron casing for forts could resist shot of 500 lbs. to 1100 lbs. from such ordnance; while the rolling of an 15 in. thick (see ARMOR-PLATE) revived the hopes of those who believe that armor will eventually vanquish guns. Finally, the forts are nearly finished, of a granite core, surrounded by a great thickness of iron plates. Above each fort are, revolving turrets carrying 35-ton guns, which throw shells of 700 lbs. The inner line of defense has been strengthened by new works at Gilkicker, Southsea Castle, etc., and by the increase in the size of the guns, and the addition of iron shields in the embrasures.