58 ANNUAL OF SCIENTIFIC DISCOVERT. 



flat-head shot of five inches diameter would begin to bear upon less 

 than one square inch of plate if it struck across a furrow, while if it 

 struck upon a corrugation, the surface pressed upon, even with a seven- 

 inch shot, would be seven square inches instead of thirty-nine, which is 

 the area of impact of a shot of this diameter upon a flat surface*. In a 

 large proportion of hits the shot would have to cut through in an ob- 

 lique direction about six inches of metal before reaching the plain plate. 

 The advantages of the plan proposed are, besides the protection of the 

 ships, the reduction of the weight of armor much below that contem- 

 plated for the new.ships of war. The saving of at least one inch in 

 thickness of plates would give a reduction of 100 tuns ; and if it should 

 be found that timber backing can with this armor be dispensed with, 

 a point now so much the subject of inquiry, the reduction of weight 

 would be about 250 tuns in a ship of the Warrior class. The extra 

 cost would be to a great extent met by the saving in the thickness of 

 plates and the timber backing. 



Interesting English Experiments with Iron-targets, Whitworth and 

 Armstrong guns. Some interesting experiments with guns and ar- 

 mor-plates, made under the direction of the British ordnance board, have 

 been reported during the past year. The following account of trials 

 on the 3d and 1 7th of March, at Shoeburyness, will be found especially 

 worthy of notice. Upon the first named date, four guns were tried, 

 viz: One of Whitworth's, of 71-inch bore, with hexagonal rifled 



Zi * > 



grooves; one Armstrong 9-inch smooth-bore, and one 10|-inch bore, 

 rifled ; also one of Thomas's rib-rifled 7-inch bore. The target con- 

 sisted of several iron plates, 5, 6, 7 and 8 inches in thickness, 20 

 inches in width, and 8 feet in length. It was 11 feet in width and 

 8 feet high, with an embrasure of 31 by 21 feet. The plates Avere 

 fastened to huge bars of iron, placet! vertically and crosswise, secured 

 with 3-inch through bolts, screwed up behind. This target represented 

 the strongest experimental gun-shield which has yet been constructed. 

 The first experiment was made with Whitworth's 7-inch muzzle-load- 

 ing rifled gun, weighing 71 tuns, and nominally throwing a 120-pound- 

 er shot, though in reality made for projectiles of the weight of 150 

 Ibs. and upward. This was loaded with 25 Ibs. of powder and a flat- 

 headed hardened projectile, weighing 137 Ibs. It struck on the left 

 side of the target with terrific force, emitting, at the moment of con- 

 tact, a sheet of flame as broad and vivid as if another cannon had been 

 fired from, the mark in reply. The massive bar frame of 12 inches 

 solid iron behind the plates was dislodged, and an 8-inch plate was 

 cracked. The impact velocity of the shot was 1,240 feet per second. 

 The next shot was from the Armstrong 9-inch smooth-bore, with a 100- 

 pound round shot of wrought-iron, and a charge of powder of 25 Ibs. 

 The missile struck full upon the thick side of the target with a velocity 

 of 1,470 feet per second, inflicting a tremendous circular dent 2^ 

 inches deep, cracking one of the inner plates of the target, and knock- 

 ing ofT one of the massive bolt-heads. The target was roughly shaken, 

 but not pierced. 



A new bolt was screwed into it and the third shot was fired from the 

 10|-inch Armstrong shunt-rifled gun. This piece of ordnance weighs 

 ll|tuns. It is rilled with 10 deep grooves on the shunt principle 

 the shot enters freely by the muzzle down one series of grooves, but it 



