MEMOIR OF DANIEL TREADWELL. 447 



above-enumerated particulars, for as to Armstrong's inventions in rifling and breech-loading he 

 deserves, in my opinion, nnich credit for them, and I hope 1 shall be the last man to deny to 

 another all that belongs to him. 



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

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

 made a strong lodgment in my mind. I had early seen that the principal objection made to 

 adopting my cannon lay in its price, and in the skill and attention that must always 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 hoo])S placed upon it under gi-cat 

 strain. I determined, by calculation, that tliis would be nearly, porliaps quite, as strong as my 

 abandoned form, would come witltin the reach of ordinary slvill, and would be in the long run 

 cheaper than the ordinary cast-iron gun." 



" I propose," continues Professor Treadwell, " to form a body for tlie 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 correspond- 

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

 embraced by another layer. These hoops are made a little less, say fxTTO^^^ P"-'"*' ^^ their diam- 

 eters less, upon their insidcs than the parts that they enclose. They are then expanded by heat, 

 and, being turned on to tlicir places, suffered to cool, when they shrink and compress, first the 

 body of the gun, and afterwards each successive layer all that it encloses. These layers of 

 wrought iron or steel hoops are placed upon the gun under yreat 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 screws 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 sul)jccted 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 as I know, 



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

 No. 10,013, was printed in 18.54. The patent was taken nut in the name of Thoiiia.s Aspinwall, then American 

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

 him. It occupies twenty-one large printed pages, with full references to elaborate drawings, which occujiy a large folio 

 plate, of the machinery used by me in constructing the cannon. [See reduced plate in Appendix, No. Ill,] Any one 

 acquainted with what Armstrong calls his gun, and the mode of constructing it, will find here everything relating to 

 it so far as its structure, n'ithoiit rijUng and brceeh-loadi)ig apparatus, is concerned. There is no diff(M-ence whatever 

 in the form of the oonstruction, the mode of putting the rings together within tlie furnace, or the tools and enginery 

 required for the work except the substitution by Armstrong of a steam hammer for tlie hydrostatic press used Ijy me. 

 Now Armstrong has shown, by his denunciation of patents, to the British Association, that he is well read in the 

 record of them; is it then probable that tliis has been overlnoked by him?" — Memoirs of Academy, Vcd. IX., 18G4. 

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



