ARTILLERY 233 



1. The iron constituting the integrant parts is all in moderate-sized, straight, pris- 

 matic pieces, formed of rolled bars only ; hence, with its fibres all longitudinal, per- 

 fectly uniform, and its extensibility the greatest possible, and in the same direction in 

 which it is to be strained ; it is, therefore, a better material than any forged iron can, 

 by possibility, be made. 



2. The limitation of manufacture of the iron, thus, to rolling, and the dispensing 

 with all massive forgings, insures absolute soundness and uniformity of properties in 

 the material. 



3. The limited size of each integrant part, and the mode of preparation and com- 

 bination, afford unavoidable tests of soundness and of perfect workmanship, step by 

 step, for every portion of the whole: unknown or wilfully concealed defects are 

 impossible. 



4. Facility of execution by ordinary tools, and under easily obtained conditions, 

 and without the necessity either for peculiarly skilled labour on the part of ' heavy 

 forgemen,' or for steam or other hammers, &c., of unusual power, and very doubtful 

 utility ; and hence very considerable reduction in cost as compared with wrought-iron 

 artillery forged in mass. 



6. Facility of transport by reduction of weight, as compared with solid guns of the 

 same or of any other known material. 



6. A better material than massive forged iron, rolled bars are much more scien- 

 tifically and advantageously applied ; the same section of iron doing much more resist- 

 ing work, as applied in the gun built-up in compressed and extended plies, than in 

 any solid gun. 



7. The introduction thus into cannon of a principle of elasticity, or rather of elastic 

 range (as in a carriage-spring divided into a number of superimposed leaves), greater 

 than that due to the modulus of elasticity of the material itself; and so acting, by dis- 

 tribution of the maximum effort of the explosion, upon the rings successively recipient 

 of the strain during the time of the ball's trajet through the chase, as materially to 

 relieve its effects upon the gun. 



Considerable attention has been given, of late years, to the construction of very 

 powerful pieces of ordnance. Cast-iron cannon are usually employed, but these very 

 soon become useless when exposed to the sudden shocks of rapid firing. Cast-iron is, 

 comparatively speaking, a weak substance for resisting extension, or for withstanding 

 the explosive energy of gunpowder, compared with that of wrought-iron, the proportion 

 being, as 1 is to 5 ; consequently, many attempts have been made to substitute wroughi- 

 iron cannon for cast. 



A gun, exhibited in 1851 by the Belgian Government, made of cast-iron 'prepared 

 with coke and wood,' was said to have stood 2,116 rounds, and another, 3,617 rounds, 

 without much injury to the touch-hole or vent. Another is said to have been twice 

 ' rebouched,' and has stood 6,002 rounds without injury. As few guns of cast-iron 

 will stand more than 800 rounds without becoming unserviceable, this mode of pre- 

 paring the iron appears to be a great improvement. At St. Sebastian 2,700 rounds 

 were fired from the English batteries, but, as was observed by an eye-witness, ' you 

 could put your fist into the touch-holes.' Colonel James, K.E. 



In Prussia they have for some time made cannon of ' forged cast-steel.' To get over 

 the difficulty of forging the gun with the trunnions on, the gun has been made without 

 them, and a hollow casting with trunnions afterwards slipped over the breech, and 

 secured in its proper position by screening in the cascable. The tenacity of this metal 

 must be very great. 



CASTING OF GUNS. Guns have long been cast in a vertical position, and with a cer- 

 tain amount of ' head of metal ' above the topmost part of the gun itself. One object 

 gained by this (of great value) is to afford a gathering-place for all scoria, or other 

 foreign matter ; an end that might be much more effectually accomplished were the 

 metal always run into the cavity of the mould by ' gaits ' leading to the bottom, or 

 lowest point, in place of the metal being thrown in at the top, with a fall, at first, of 

 several feet, as is now the common practice, by which much air and scoria are carried 

 down and mixed with the metal, some of which never rises up again, or escapes as 

 ' air-bubbles.' 



The value of the ' head of metal ' in casting of guns is shown by the following 

 Table, constructed by Mr. Robert Mallet, after a series of carefully conducted ex- 

 periments, which he published in a paper entitled ' On the Physical Conditions involved 

 in the Construction of Artillery ' :~ 



