MEMOIR OF DANIEL TKEADWELL. |J7 



merated 



deserves, in my opinion, much credit for them, and I hope 1 shall be the last man to dun lo 



another all that belongs to him. 



"Although I was thus obliged to suffer the loss and shame of defeat, and abandon all thai I 

 had done, the mechanical theories upon which I had wrought and developed in practice bad 

 made a strong lodgment in my mind. I had early seen thai the principal obj '.turn made to 

 adopting my cannon lay in its price, and in the skill and attention that must alwaj I be required 



in its manufacture. To obviate these I proposed to myself to form a cannon of a thin cast-iron 



body surrounded by several layers of wrought iron or steel hoops placed upon it under gnat 

 strain. I determined, by calculation, that this would be nearly, perhaps quite, as strong as mv 

 abandoned form, would come within the reach of ordinary skill, and would be in the long run 

 cheaper than the ordinary cast-iron gun." 



"I propose," continues Professor Tread well, "to form a body for the gun, containing the 

 calibre and breech as now formed, of cast-iron with walls of only about half the thickness of the 

 diameter of the bore. Upon this body I place rings or hoops of wrought iron, in one, two, or 

 more layers. Every hoop is formed with a screw or thread upon its inside, to fit to a < invspond- 

 ing screw or thread formed upon the body of the gun first, and afterwards on each lay< r that is 



embraced by another layer. 



uWi 



eters less, upon their insides than the parts that they enclose. They air then expanded by beat, 

 and, being turned on to their places, suffered to cool, when they shrink and compress, first th 

 body of the gun, and afterwards each successive layer all thai if encloses. These layers of 

 wrought iron or steel hoops are placed upon the gun under great strain." * 



He laid great stress upon the accurate adaptation of the screw of the body to that 

 of the hoop ; he considered the difference between the thread of a screw cut cold, 

 and the same thread when heated, and devised a machine for making screu- with 

 slight differences to obviate this very difficulty. A model of the machine is in the 

 Observatory of Harvard College. 



" The great idea which I followed in this construction is to place the material of which it is 

 composed in an abnormal condition, that is, to place the inner portion under a state of com- 

 pression, and the external portion or hoops under a state of great strain; and this is done to 

 provide against the difficulty to which all cannon having their materials in a condition of equi- 

 librium are subjected by the explosive effect of the powder rending the internal portion before 

 any considerable strain is thrown upon the external portion. This condition, so far a.> I know, 



which is in the Boston Library ; and I there find that the specification of my English patent, enrolled July 5th, 1844, 

 No. 10,013, was printed in 1854. The patent was taken out in the nam, of Thomas Aeprowall, then American 

 Consul at Louden, who acted as my attorney. This specification was written by me, and transmitted complete to 

 him. It occupies twenty-one large printed pages, with fall references to elaborate drawings, which ocenpy a la. folio 

 plate, of the machinery used by me in constructing the cannon. [See reduced plate in Appendix, No. III.] Any on< 

 acquainted with what Armstrong calls lus gnn, and the mode of constructing it, will find here everything n-latir .« to 

 it so fur as its structure, without rifling and breech .-loading apparatus, is concerned. There is no difference whatever 

 in the form of the construction, the mode of patting the rings together within the furnace or the tools and enginery 



Arm 



record of them; is it then probable that this has been overlooked by him !»- Memoirs of Academy, Vol. IX, 1864. 

 * See page 412 for method of making trunnion-bands in 1841-44. 



