454 MEMOIR OF DAXIEL THEADWELL. 



under the light of my former experience to devise a practicable method of fabricatin.ff guns of 

 enormous size, that must fulfil all the conditions reqiured for continued service. 1 forwarded to 

 you some weeks since through the Smitlisonian Institution a copy of the memoir in which I have 

 examined the subject in detail and, as I think, demonstrated the perfect practicability of making 

 a really great step in the power of artillery. I hope that you have found time to read this 

 memoir, and if so 1 feel sure that, with your former views of the importance of the subject, you 

 will not be disposed to let the improvement die. I have already in my former experiments 

 expended too much time and money to dare again to enter upon it practically without official aid. 

 Knowing the just influence that you must possess with the Government, from tlie confidence 

 universally reposed in your great knowledge, may I not hope that you will give a project so 

 accordant with your own ideas such an examination as its importance demands. An appro- 

 priation of a few thousand dollars would, I am perfectly confident, produce an instrument vastly 

 sui)crior to anything before known, and point out the true way of rendering our ports and sea- 

 coast entirely unassailable. 



Very respectfully your obedient servant, 



Daniel Treadwell. 



We have seen what became of the Treadwell gun of 1854 at the hands of our 

 own Government. Let us now see what has become of it in the hands of other 

 governments and other manufacturers, and for this purpose we will compare the 

 methods of construction adopted elsewhere with those of Professor Treadwell above 

 described. 



Colonel E. Maitland, Royal Artillery, thus describes the methods of Armstrong as 

 practised at Woolwich and Elswick in 1880, twenty-six years after Treadwell's 

 pubhcation. These guns are known as " built-up guns." 



" Wrought-iron coils are shrunk over one another so that the inner tube is placed in a state 

 of compression and the outer portions in a state of tension, an endeavor being made to so regulate 

 the amount of tension that each coil should perform its maximum duty in resisting the pressure 

 from within. Further, the fibres of the several portions are so arranged as to be in the best 

 positions for withstanding the pressures. It must be noted that a wrought-iron bar is about 

 twice as strong in the direction of the fibre as across it. The exterior of the gun is therefore 

 constructed of coiled bars of wrought iron welded into hoops and shrunk one over the other, 

 thus disposing the fibre to resist tlie circumferential strain. These outer coils are shrunk over a 

 hollow cylinder of forged iron, having tlie fibre running Icngthway so as to resist tlie longitudinal 

 strain. Within this cylinder, a forged breech piece, is placed a steel tube, gripped in like manner 

 by shrinkage. This grand principle of gun construction is carried out by turning tlie inner coil 

 in a lathe to an exterior diameter slightly greater than the interior diameter to which the outer 

 coil is bored. The outer coil is expanded by the application of heat and slipped over the inner 

 one. It contracts on cooling, and, if the strength of the two coils is properly adjusted, tlie outer 

 will remain in a state of tension, and tlio inner in a state of compression. The number of coils 

 is not limited. ... 



" In making these coils blooms of iron arc rolled into flat bars, which are fagoted together 

 and rolled into long bars of the section required for the part of the gun for which they are 



