MECHANICS AND USEFUL ARTS. 65 



form an iron wedge, twenty-one inches thick at the base, and termi- 

 nating in a sharp edge. This wedge is sustained by the plates behind 

 it, ten and a halt' inches in thickness, six feet in depth, and extending 

 the whole length of the vessel, forming the most powerful butting in- 

 strument that it is possible to conceive of. Captain Ericsson says, 

 " It will split an iceberg." 



Some interesting additions to our knowledge respecting the resist- 

 ance of iron plates to projectiles have been gained from the experi- 

 ence of iron-clad vessels upon western rivers of the United States. 

 In the construction of the Essex, the flag-ship of Commodore Porter, 

 a peculiarly prepared lining of India-rubber was placed between the 

 one-inch iron plates used and the wooden backing. The efficacy of 

 this expedient was demonstrated on the 22d of July, 1862, when the 

 Essex, under the batteries of Vicksburg, sustained for two hours and 

 a half a fire of seventy heavy guns in battery, twenty field-pieces, 

 and three heavy guns afloat. So rapid and terrific was the fire that 

 the commodore, in his official report, states " that for half an hour 

 the hull of the ship was completely enveloped in the heavy jets of 

 water thrown over hr by the enemy's shot, shell, and balls." At one 

 time this cannonading was at so short a range that he says " the flashes 

 of the enemy's guns through my port-holes drove my men from the 

 guns." The results of this fire from batteries not one hundred feet 

 off is thus described in the official report: "A heavy ten-inch 

 shot from the nearest battery struck my forward casemate about four 

 feet from the deck, but fortunately did not penetrate. A rifle seven- 

 and-a-half-inch shot from the same battery struck the casemate about 

 nine feet from the deck ; it penetrated the iron, but did not get 

 through, although so severe was the blow that it started a four-inch 

 plank, two inches thick and eighteen feet long, on the inside. A 

 conical shell struck the casemate on the port side, also, as we were 

 rounding, penetrated the three-quarter-inch iron, and came half way 

 through the wooden side ; it exploded through, killing one man and 

 slightly wounding three." 



During the heavy cannonading most of the shot glanced from the 

 sides of "the Essex, but " during that time this vessel was heavily 

 struck forty-two times and only penetrated twice." This penetration 

 was by the rifle seven-and-a-half-inch shot and the conical shell above 

 described. 



James's rifled Projectile for Battering Purposes. The bombard- 

 ment of Fort Pulaski demonstrated the extraordinary efficiency of 

 James's projectile for battering down stone-work. The New York 

 Times correspondent, describing its effects, says: " The whole side 

 of the casemate was shot away. The Parrott guns had been compar- 

 atively harmless, the work being done almost entirely by the James 

 projectile." Another correspondent, writing from the ruins of Pulaski 

 to the New York Tribune, says: "The guns which contributed 

 most to the breaching of the wall were those which carried the James 

 projectile. That was the testimony of the officers of the fort ; and in 

 the thickest of the ruins it was always these shot which we found 

 most abundant." A private letter, written by an officer, says, " This 

 shot bored through a massive brick wall, and ground up the material 

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