MEMOIR OF DANIEL TRBADAVELL. 



•id 



"By attention to the preceding statement, we s. e thai two distinct quest ious are brought 

 up for examination. First, Docs the expansive fluid, formed ol fired gunpowder, < \< i an 

 equal force in every direction? and, secondly, Does a cann u. of the usual form, pn mi in 



every direction an equal area of metal, acting with an equal mechanical advantage, to be 

 torn asunder before the fluid can escape? We may, I think, for all practical purposi . ; tee it 

 as true, that the expansive force of fired gunpowder is equal in all directions, and that, <<>n- 



sequently, no advance could be gained by giving any particular direction to the 6br * oi the 



wrought iron of which a cannon should be made, depending upon the force of the fluid being 

 less in one direction than in another. 



"To answer the second question, namely, Does a cannon of the usual form prei at, in e\. r\ 



direction, an equal area of metal, to he torn asunder before the fluid can escape? we shall 

 find it useful to resort to numbers, and apply them to a form as an example. For this pur- 

 pose, let us suppose that we have a hollow cylinder, say twelve inches Ion-, the calibre being 



one inch in diameter, and the walls one inch thick, giving an external diameter of thn «• inch i. 

 Suppose this cylinder to be perfectly and (irmly closed at its ends l>\ ren plugs, or am other 

 sufficient means. Let this be filled with gunpowder and fired. The iluid will exert an equal 

 pressure, in every direction, upon equal surface- of the sides and ends of the hollow cylinder. 

 Let us next examine the resisting power of a portion of this cylind r, say one inch long, 



situated in the middle, or equally distant from the ends, so that it shall not be strengthened 



by the iron which is beyond the action of the powder. The fluid, enclosed by tins ring of one 

 inch long, contains an area of one square inch, if a section be made through it in the direction 



of its axis; and the section of the ring itself, made in the same direction, will ni sure Iwo 

 square inches. "We have then the tenacity or cohesive force of two square inches of iron in 

 opposition to an area of the fluid measuring one square inch; and if we take the tenacity of 

 the iron at 65,000 pounds, the cylinder will not be burst, in the direction of its length, unh ■* 

 the expansive force of the fluid exceed 130,000 pounds to each inch. Next, let us suppose a 

 section made through the cylinder and fluid transversely. The area of the fluid, equal to the 

 square of the diameter of the hollow cylinder, is one circular inch, and the area of the whole 

 section is, the diameter being three inches, nine inches. Deduct from this the area of the 

 calibre, and we have eight circular inches. That is, the section of the iron is eight times 

 greater than that of the fluid ; whereas in the former case of longitudinal section the iron 

 gave but twice as much surface as the fluid, and if we take, as before, the iron at 65,000 

 pounds per inch cohesive force, it will not be broken unless the force of the thud exceed 

 520,000 pounds. It will be found, upon a further examination, that the relations of these 

 sections to each other may be varied, as we take the diameter of the calibre to be greater or 

 less, as compared with the thickness of the sides, but their dill pence can never be made less 



than as two to one. Here then is a principle, or rather a fact, of the utmost importance in 

 forming cannon of any material, the strength of which is different in different din tions; for as 

 a cannon made in the proportions above specified, if the materials be in all direction- of equal 

 strength, will possess four times as much resistance to across fracture as it does to re at a 

 longitudinal fracture, it follows that a fibrous material which possesses four t i in the strei ;th 

 in one direction that it does in another will forma cannon of equal strength if the fibres be 

 directed round the axis of the calibre. It is this fact which gives the great superiority to the 

 various kinds of twist gun-barrels. For in these, although the fibres do not inclose the calibre 

 in circles, yet they pass around it in spirals, thus giving their resisting force a diagonal direc- 

 tion, which is vastly superior to the longitudinal direction in which the fibres are arranged 

 in a common musket-barrel. 





