MEMOIR OF DANIEL TREADWELL. 455 



intended. These bars are tlicn placed in a long narrow, reverberatory furnace, and raised to a 

 briiiht red heat. Wiieu ready fi)r coilint^, one end is drawn ont and fixed to a revolving man- 

 drel, wliich pulls the bar out and winds it into a coil, like a rope round a eajistan ; it is then again 

 heated and welded under a steam hammer: on cooling, it is bored and turned to the proper 

 dimensions." 



The Krupp gun also has a steel tube, but much thieker than the Armstrong gun, 

 and in this respect still more nearly approaching the Treadwell pattern, with cast- 

 iron body ; over a considerable portion of the chase, hoops of cast steel are shrunk, 

 the shrinkage being so adjusted that the successive layers of hoops shall support the 

 body of the gun. The number of the hoops depends upon the size of the gun, 

 usually greater than that of the English coils. They are secured in their places 

 on the body by a number of splines, which prevent movement. The details of the 

 manufacture of the Krupp guns have not been made public. It is not known 

 that the Treadwell method of hammer hardening the hoops to restore their elas- 

 ticity after heating is practised by Krupp; nor is it known that he used Mr. 

 Treadwell's method of employing heated oil to determine the limit of tempera- 

 ture to which they should be heated when they are placed in position on the body 

 of the gun. 



Captain T. A. Blakely made a tube of cast iron resembling a gun, and over it 

 forced with a hydraulic press one or more tubes accurately turned on the inside, of 

 wrought iron. A gun thus made with hoops scarf-welded successfully resisted more 

 than ordinary charges. Subsequently, after 1854, he adopted Treadwell's method of 

 heating tlie rings and shrinking them on the body. 



The Russian government has a foundry for guns of large calibre. These guns 

 have a body of steel upon which are shrunk hoops also of steel; a twelve-inch gun 

 weighing 89,296 pounds has forty-seven hoops. 



The Whitworth gun is in its essentials made after the method of those just de- 

 scribed. As already stated, he prefers, like Treadwell, hydraulic pressure to the 

 steam hammer for his forgings. 



Comparing these cannon with those made by Treadwell for our own Government 

 in 1842, and those of his specification in 1854, we cannot but be struck with their 

 close resemblance, both in the principles and method of construction. They are 

 in fiict substantially the same, — the same principles and methods upon which the 

 strongest and most enduring guns are now made. The making of the hoops by wind- 

 ing the bar like a rope on a capstan, instead of a ribbon on a block, is not material as 

 to strength. Indeed, as we have already said of the guns of 1842, we may now sny 

 of the sjuns of 1854 : if all knowledge of Armstrong's methods were lost, they could 



