involved in the Construction of Artillery. 399 



practically caiTying out the consequences of taking up recoil in field-guns, not by inertia, 

 but by elasticity, as productive of future results, in connexion with wrouglit-iron guns 

 and improved ammunition, likely to revolutionize our existing field artillery. 



Note U.— (Sect. 270.) 



The American Reports contain some interesting accounts ol' their methods of mav'in" 

 musket barrels by water pressure ; but there are no systematic results as to the relation of 

 resistance to fluid pressure from within, to diameter and thickness of metal. 



The experiments of Lieut. Hagner, U. S. A., indicate that the best musket barrels will 

 not sustain, witliout injury, a steady and continued water pressure of above (5400 to GSOOlbs. 

 per square inch of internal surface ; and, taking the section of resisting metal from the 

 thinnest part of the barrel exposed to the pressure, the strain per square inch of section 

 of wrought-iron due to this pressure is about 25,500 lbs. So that, even on these thin 

 cylinders, the rupturing strain is much below that of direct tension, which, for the iron of 

 tliese barrels (Salisbury, U. S.), is given at 66,000 lbs. per square inch. 



Note V.— (Sect. 271.) See Note T. 



Note W.— (Sect. 282.) 

 Resistance of Cylinders to Fluid Pressure from ivithin. 



For the following original investigation 1 am indebted to my learned friend, A. S. Hart, 

 Esq., LL. D., Fellow of Trinity College, Dublin, whose attention was directed to this subject 

 by my questioning the correctness of Professor Barlow's deductions from his own theory, and 

 stating to him (though imperfectly and incompletely) my own views as to the effects of 

 distance from the a.xis upon the effective resistance of any given lamina. 



With his permission I place it in this Note, and gladly avail myself of the opportunity 

 of acknowledging the advantages I have derived, on this and other subjects, from his great 

 mathematical ability. 



" The cylinder may be considered as consisting of a series of cylindrical laminre, the 

 inner of which is extended by the pressure of the fluid, part of which pressure is sustained 

 by the resistance of the first lamina, and part transmitted to the next, and so on. 



3f 2 



