352 Mr. Mallet on the Physical Conditions 



Note D. — (Sects. 3, 4.) 



MncH remains to be ascertained by experiment as to the law of development of the pres- 

 sure produced by the gases of the inflamed powder up to its maximum, before analysis can 

 do much to advance our knowledge in a way to be practically useful in proportioning the 

 strength of guns. 



Poisson published, from the MSS. of Lagrange, some important investigations on this 

 subject in torn, xiii., p. 187, &c., of the "Jour, de I'Ecole Polytech." — "Mem. sur les 

 Relations au Movement du boulet dans I'interieur du Canon ;" and General Piobert has 

 also brought his great mathematical and practical powers to bear upon the subject; but, 

 partly from the algebraic difficulties of the question, and partly from want of data, which can 

 only be obtained by entirely new methods of experiment, much is yet required to enable 

 practical formulae to be deduced. 



The proposition of the text, which will be found further sustained by the investigation 

 in the subsequent Note S, shows the fallacy in theory of several projectors, who, within the 

 last five years, propose to reduce the strain upon artillery, the weight of shot being given, 

 by conjoint diminution of caliber, and the use of elongated shot, under the notion that guns 

 of reduced thickness can thus be made to answer. 



At the same time, the valuable practical result must be admitted, in the unity and sim- 

 plicity of artillery, should it be possible to construct guns of wrought-iron, or in any way, 

 of such strength that they should bear to be fired at pleasure, when required, either with 

 spherical or with elongated shot, of greatly increased weight. In many of the trials of elon- 

 gated shot that have been made, with unfavourable results, at Woolwich, a great theoretic 

 oversight appears to have prevailed, in continuing to use the same proportionate weight 

 of powder for propulsion as with round shot, — one of the most important advantages 

 offered by elongated shot being thus lost, viz., that their great momentum, and proportion- 

 ably small aerial resistance, gives an equal or greater range, with a much lower velocity, 

 than with spherical shot ; and that hence the old proportionate charge of powder is not 

 only unnecessary and wasteful, but destructive in its action upon the gun, before the inertia 

 of rest of those heavy shot can be overcome. (See " Artillerie Nouvelle, par M***», Cap. 

 de Artill." Paris, 1850, p. 18.) 



The observations made in the United States, upon the point of greatest wear by deflagra- 

 tion, in the interior of the chase of Colurabiads (8-inch guns), throw some approximate light 

 upon these questions, indicating, as they do, that the spherical shot does not begin to move 

 until a large portion, at least, of the powder is ignited, and moves through, from a quarter 

 to one half its diameter, before the ignition of the whole is completed. 



In the reference to this Note from Section 256, see also Note I., referring to Section 60. 



