PROCEEDINGS OP THE POLYTECHNIC ASSOCIATION. 49t 



experiments were made in St. Louis, Missouri, in the months of February 

 and March, 1S63, with the following: results : 



Fird. A conical ball of lead, weighing half an ounce, was fired at a tar- 

 get of pine wood, covered with a plate of iron one-sixteenth of an inch in 

 thickness, at a distance of eighty feet, and at an angle of forty-five de- 

 grees ; the ball penetrated the iron, and went several inches into the wood. 

 Then one-fourth of an inch of vulcanized India rubber was placed behind 

 the iron plate, and at the same range and angle a ball of similar dimen- 

 sions, and same charge of powder, merely indented the iron plate, without 

 penetrating through it ; this was repeated in like manner several times 

 with similar results. 



Second. A steel bolt, one inch in length, and 9-16 inches in diameter, 

 weighing- one 21-480 ounces, was fired from an Enfield rifle, with a full 

 "charge of powder, at a plate of iron three-eighths of an inch in thickness, 

 backed by four inches of oak. This bolt penetrated the iron plate, and 

 Stuck into the wood backing, but rebounded at an oblique angle with 

 great violence, without penetrating the plate when a plate of vulcanized 

 India rubber half an inch in thickness was placed between the iron plate 

 and wood ; this was also repeated with similar results. The range in these 

 experiments was fifty feet. It was then determined to place "mixed," or 

 fibrous "India rubber" plates under the armor plates of the forward case- 

 mate of the gunboat Essex, then in process of reconstruction. Her case- 

 mates were erected on the gun deck, at an angle of forty-five degrees, and 

 were covered with iron. The forward casemates were composed of twenty- 

 six inches of oak, and one inch of India rubber, covered with iron plates one 

 inch in thickness the after casemates were of oak sixteen inches, covered 

 with similar armor plates ; the midship case mates were also of oak and 

 pecan, of similar thickness, covered with iron plates three-fourths of an 

 inch in thickness. Neither of the latter portions of her casemates were 

 covered with India rubber. The armor plates were all manufactured from 

 similar stock of metals, and by one party. 



In the action between this gunboat, commanded (at that time) by Com- 

 modore W. D. Porter, and the batteries at Vicksburg, Port Hudson, and 

 other points on the lower Mississippi river, the forward casemates were 

 struck repeatedly by solid shots, varying from thirty-two to one hundred and 

 twenty-eight lbs., some of which were fired from rifle guns at s hort range. 

 None of those shots penetrated the forward casemates; but some of the 

 larger ones indented the armor plates, started the wood work, and broke in 

 pieces, showing that the force of the shot was entirely spent. 



The after casemates, covered with iron of the same thickness, made by 

 the same manufacturers, but without India rubber, were penetrated in 

 several places by shots fired from the same batteries, and similar guns ; in 

 all, over one hundred and twenty-five shots, struck this vessel at about the 

 same range, proving that this thickness of iron affords no protection when 

 placed immediately upon a solid timber support. In fact, the same may be 

 said of two and a half and three inches of iron, if we may form a correct 

 judgment from the results of the actions between the gunboat Galena and 



[Ail. Inst.] G* 



