400 777^ SCIENTIFIC PAPERS OF 



gun, steel only should be used, in which the strains should, if 

 possible, be so distributed that when the powder pressure acts, 

 each portion should offer the same resistance to the strain. This, 

 I think, might be effected in a very thorough manner by a process 

 analogous to that employed by Admiral Eodman in the construc- 

 tion of cast-iron guns, only that cast-iron is perhaps the material 

 least adapted for the purpose. If a steel gun or a ring forming 

 part of the same was put into a furnace, heated up to a tempera- 

 ture of say 600 C., and the inside was subjected to cooling action, 

 while the outside was maintained at the temperature of the fur- 

 nace, a distribution of stress would result which would be highly 

 advantageous to the strength of the gun. The chilling of the 

 inside surface of the ring or gun would cool the metal towards the 

 inside circumference. This metal could not shrink, nor would the 

 inner diameter of the gun diminish, because the diameter would 

 be determined by the mass of metal still in the heated condition. 

 The vacancies produced in the cooled metal would be filled up by 

 the inflow of metal from the heated mass outside, resulting in 

 equilibrium of the metal at the diameter originally due to the 

 heated mass, and the temperature will gradually vary from say 

 100 inside to 600 outside. If the gun was afterwards taken out 

 and allowed gradually to cool, but without stopping the cooling 

 action from within, the whole mass will cool down to the minimum 

 temperature. If we imagine the ring to consist of a succession of 

 concentric cylinders, each cylinder would acquire a tensile strain 

 due to its previous temperature, which being a minimum on the 

 inside and a maximum on the periphery, there would result a 

 distribution of tension throughout the mass, being negative or 

 compressive in the interior and more and more tensile towards 

 the exterior. Then when the full pressure of powder gas was 

 active, the strain upon each portion would be equal, and the 

 resulting strain would be opposed by the whole elastic strength of 

 the metal. The internal portion of the tube would, with such a 

 mode of construction, have no other function to perform than to 

 resist the abrasion that is necessarily going on in the gun. This 

 question is just now very much before the scientific public, and 

 therefore I thought it well to bring before you my own view of 

 the matter. 



Before quite concluding, I would call attention to a machine 



