NATURAL PHILOSOPHY. 175 



its under side to compensate for the weight of the ball. It would seem im- 

 possible that in this condition the ball, receiving the pressure of the powder 

 equally distributed in the direction of the axis of the calibre, should touch the 

 gun more than by a slight graze during its flight.* 



Unless this or some equally efficient remedy is adopted, any considerable 

 increase in the*size of cannon must be hopeless; for a surface as hard as a 

 smith's anvil would give way under the long-continued pounding of naked 

 twelve-inch shot ; and whenever hooped cannon may be made and used, it 

 will be essential that the means of preventing the lodgment herein given be 

 always and at all times carefully applied. 



Pressure of Fired Gunpowder. It is well understood that the pressure of 

 the explosion in a gun is greatest at the beginning, and gradually dies away 

 as the ball moves forward ; but this depends much on the combustibility of 

 the powder. With good quick powder the pressure at the instant the powder 

 is fired is immense ; but until recently no one has been, able to measure it. 

 Dr. TV r . F. Woodbridge and Major Alfred Mordecai have been recently 

 making some experiments at the expense of the U. S. Ordnance Department, 

 for testing this point, at the Arsenal in Washington. With a ball weighing 

 about 6lbs. and a charge of llb. of Dupont's cannon powder, the greatest 



* My observations upon the lodgment have been made upon wrought iron cannon. Be- 

 tween the years 1841 and 1S45, I made upwards of twenty cannon of this material. They 

 were all made up of rings, or short hollow cylinders, welded together endwise. Each ring 

 was made of bars wound upon an arbor spirally, like winding a ribbon upon a block, and 

 being welded and shaped in dies, were joined endwise, when in the furnace and at a 

 welding heat, and afterwards pressed together in a mould by a hydrostatic press of 1,000 

 tons' force. Finding in the early stage of the manufacture that the softness of the wrought 

 iron was a serious defect, I formed those made afterwards with a lining of steel, the 

 wrought iron bars being wound upon a previously formed steel ring. Eight of these guns 

 were C-pounders of the common United States bronze pattern, and eleven were 32-pound- 

 ers of about 80 inches length of bore, and 1,800 pounds weight. Six of the 6-pounders, 

 and four of the 32-pounders, were made for the United States. They have all been sub- 

 jected to the most severe tests. One of the 6-pounders has borne 1,560 discharges, begin- 

 ning with service charges and ending with 10 charges of 6 pounds of powder and 7 shot, 

 without essential injury. It required to destroy one of the 32-poun ers a succession of 

 charges ending with 14 pounds of powder and 5 shot, although the weight of the gun was 

 but 60 times the weight of the proper shot. If any of these guns are ever destroy -d by 

 firing them, the destruction will commence in the lodgment. 



It was during a course of experimental firing with the soft wrought iron gun, that I had 

 an opportunity of observing the formation and increase of the lodgment ; and here I was 

 led to the experiment of placing the shot in a bag, as recommended in the text. My 

 experiments were not sufficiently extended and varied to lead me to an assured conviction 

 that the evil may be entirely prevented by this practice ; but they were enough to lead 

 me to a confident expectation of that result, as I could never detect the formation of any 

 lodgment or any increase in one, previously formed when the bag was used. 



I cannot leave this subject without observing that I regard the late, and still continued, 

 attempts to make wrought iron cannon in Europe by the process of fagoting or piling as 

 a strange engineering delusion. It may not surprise us that amateur engineers, whose 

 whole knowledge of the character of iron is derived from a printed page, should expect 

 useful results from this attempt, but that men practically acquainted with working iron 

 should expect to forge a serviceable gun of wrought iron by the same process that is used 

 to produce a shaft of that material, seems to me not very creditable to the iron knowledge 



of the age. 



