ON METALS FOR ORDNANCE. 105 



provided this could be accomplished and the core kept cool by a current of 

 air or water, as is said to have been done in America, considerable improve- 

 ment as regards strength would be effected. If these suggestions were acted 

 on, the Government of this country would doubtless have guns of as great 

 strength and range as any other nation ; and it would be a disgrace to us, if, 

 with our boasted skill and vast experience in the treatment of metals, we 

 could not surmount a difficulty which should never have existed, and 

 which only requires the attention of practical men to place it on a more 

 satisfactory footing. 



In all descriptions of artillery the strain in the chamber of the gun is 

 enormous. This is evident when we consider that the ball leaves the gun 

 with a velocity of 1800 to 2000 feet per second, and that the force which 

 gives this immense velocity acts equally on the breech of the gun as upon 

 the ball. From these data we must learn to apportion the metal to the 

 several parts in the ratio of the strain they have to bear. 



The length of the bore is another important point, as, within certain 

 limits, the range depends upon the time during which the expansive power of 

 the gases of the explosion is acting upon the ball, or in other words, on the 

 length of the bore. Increasing the length of the bore increases the range, 

 or, what is the same thing, diminishes the amount of powder necessary to 

 project the ball to a given distance. 



One of the causes of failure, in both ancient and modern artillery, is the 

 abrasion of the lower part of the vent by repeated discharges. In modern 

 guns this is perhaps more injurious, on account of the porous state of the 

 metal at that part arising from casting solid. To remedy this defect it is 

 important to increase the density of the metal, and if possible to case-harden 

 the entire inner surface of the gun. To attain this we have already in- 

 timated that ordnance be cast in chill ; that is, should be cast on accurately 

 turned metallic cores, at such a temperature as is best calculated to secure 

 the object in view. To obtain uniformity in the rate of cooling round this 

 core, and to produce a hard skin of steeled iron over the whole interior of 

 the gun, the core should be hollow, and a current of air or water conducted 

 through it. This process would- secure much greater strength and durability 

 to ordnance, and at the same time cheapen its construction. 



In a former part of this Report we referred to the process of casting in 

 chill {vide page 103). This is a process well worthy of the attention of the 

 Government, as a series of accurately conducted experiments, with proper 

 apparatus, would, in our opinion, lead to important and highly satisfactory 

 results. At St. Helens experiments of this nature were made by Messrs. 

 Robinson and Cook under the immediate superintendence of Mr. Fairbairn ; 

 and judging from the results of some of the castings, there did not exist a 

 doubt as to the advantages to be derived from the system if properly carried 

 out. Several guns, or rather cylinders, of the same proportionate thickness 

 of metal were cast ; two of them failed, from some irregularities in the cooling, 

 which caused the core or mandril to get fast ; another, however, was well 

 cast, with a perfectly smooth, interior skin, case-hardened to a considerable 

 depth by the chill. In this experiment the process was to a great extent 

 successful, and the only difficulty to be encountered was the danger indi- 

 cated by the failures, of collapse or contraction upon the mandril. The 

 utmost care was required for regulating the rate of cooling upon the man- 

 dril to prevent its being unduly heated by the surrounding mass so long 

 retained in a state of liquefaction. 



In these experiments sufficient data were established to convince the 

 experimenters that, with proper tools and appliances, this system of casting 



