544 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



Rodman gun, cast hollow, and cast-iron guns band;d round the brooch with 

 wrought iron. 



17. Of wrought iron and steel guns there are three kinds: those made 

 from solid forged masses, as by Wiard in 18GI, by Krupp of soft steel, and 

 by Ames of wrought iron. Those that are barrel-banded, as by Armstrong, 

 Blakele}', Whitworth and Treadwell, and staves with bands, as proposed 

 by Mallet, and practiced from the most ancient times. Bronze guns are 

 only used for small calibres. Each kind of material fabricated can be used 

 with success, in making small guns, but for larger guns, although made in 

 the same manner, they invariably fail when subjected to the actual condi- 

 tions of service, and at this time no absolutely safe large gun is to be 

 found in any service in the world. 



THE STRONGEST METAL DOES NOT MAKE THE STRONGEST GUN. 



18. That this failure is due to other causes than inability to withstand 

 the pressure of the gases of the powder, may be found in the fact that a 

 large calibre steel gun, with a tensile strength of 120,000 pounds to the 

 inch of section, exhibits lees endurance under rapid firing than a cast-iron 

 gun of the same calibre, form and size, with a tensile strength of 18,000 

 pounds. Or 8- inch cast-iron guns made from metal having a strength of 

 38,000 pounds to the inch of section, have less endurance than a gun of 

 like calibre and form of which the iron has a tensile strength of only 

 21,000 pounds. 



19. The following extract from Rodman's work on ordnance, pages 137 

 and 138, (erasing the repetitions of the words solid-cast whenever they 

 occur,) fully illustrates this principle. It is not deemed out of place here, 

 in order to show the necessity of further investigation into the properties 

 of cast-iron, in its ap lication to the manufacture of cannon, to notice some 

 facts in the history of gun founding in this country since 1849. 



20. The very low endurance of the first pair (8-inch) of experimental 

 guns which were cast in that year, was attrbuted to the inferior quality 

 of the iron of which they were made. Two years were spent in searching 

 after a better quality of iron, which was undoobtedly found; and in 1851 

 another pair of 8-inch guns was cast. 



21. The iron in this pair of guns has a tenacit}' of near 38,000 pounds, 

 while that of tae iron in the first pair was only between 27,000 and 28,000 

 pounJs. The gun of the first pair burst at the 85th fire, and that of the 

 second pair at the 73d fire; the superior iron giving the inferior gun. 



22. These results did not, however, destroy confidence in strong iron for 

 guns, and the first pair of 10-inch guns was made from the same lot of 

 iron; and with a tenacity of iron of 37,000 pounds the gun burst at the 

 20th fire. This result weakened confidence in very strong iron, and the 

 tenacity was reduced. In 1857, after guns of good tenacity had failed at 

 Fort Pitt, South Boston, and West Point foundries, four out of seven guns 

 offered for inspection at the lust named foundry have burst in the proof. 

 Mr. Parrott, proprietor of the West Point foundry, one cf our most expe- 

 rienced gun founders, cast his trial contract guns of iron, having a tenacity 

 of 30,000 to 32,000 pounds. 



23. One of these guns has endured 1,000 service charges of 14 pounds 



