292 IMr. Mallet on the Physical Conditions 



one-third as much, leaving the opening at the instant between one voussoir and 

 the nest only '00027 of an inch. The amount of opening, therefore, would be 

 so evanescent, as to preclude the transference of any elastic pressure, into tan- 

 gential force, between the joints. Mechanical engineers, best competent to 

 judge of the question, will not hesitate to admit, that with the accuracy and 

 power of precise repetition of similar regular forms, which we now possess, in 

 the lathe and planing machine in their several modifications, no real difficulty 

 exists to the perfect formation, and scrupulously exact fitment, of these longitu- 

 dinal bars and external rings, at a very moderate cost. Indeed, Mr. Whitworth 

 has already actually accomplished incomparably more difiicult forms and fittings, 

 in the internal longitudinal shell, and external rings, of his patent rifled cannon ; 

 which, in the principles of its design, however, differs altogether from that of 

 the construction here proposed, inasmuch as the interior longitudinal shell of 

 his gun is formed in three pieces of a single thickness each, and his external 

 rings are also in a single ply or thickness, by which the entire advantage of 

 their separation into laminte, which would nearly double the strength of the 

 gun, is lost. 



288. Solid reinforce rings, indeed, have been repeatedly proposed, and fre- 

 quently applied to various projects or forms of cannon, but the author believes 

 that the peculiar advantages of their application in thin concentric lamince, the 

 internal ones of which shall be compressed, by an initial extension, of the external 

 ones, has never before been distinctly pointed out, and their adoption proposed 

 and urged ; the essential and radical distinction being this, that by no arrange- 

 ment or variation of design, can a gun be formed in a single ply of rings whose 

 strength to sustain an internal pressure shall be greater than the cohesive power 

 of the material per square inch of section ; whereas, by the subdivision of the 

 rings into a number of superimposed plies, each compressing those within it, 

 the strength of the gun may be increased so as to bear an internal pressure, 

 any required number of times greater than the ultimate cohesive power of the 

 material ; in fact, may be increased ad infinitum. 



289. The investigation (in Note Y) may appear to render the operation of 

 shriukiug-on the subdivided rings in succession, a very delicate and difficult one ; 

 and so it would be, were it in practice necessary to take any very precise ac- 

 count of the temperature at which each ring is to be placed upon the previous one; 



