104 REPORT — 1855. 



should be forged upon a mandril in a series of rings, welded successively one 

 upon another, till the required length is completed. He is of opinion that 

 the hot blast has enabled the manufacturer to produce iron from inferior 

 materials, and that quantitj-, not quality, is chiefly aimed at by the smelter. 

 He considers, however, that if premiums were oifered for the best and 

 strongest qualities of iron, Government would soon have metal of the required 

 tenacity. He recommends that guns be cast hollow with cores artificially 

 cooled. He thinks that it would be advantageous to cast a number of bars 

 about 2 feet long and 2 inches square, in moulds of various materials, as in 

 green-sand, dry-sand, loam, in chill, and in cast-iron moulds at 500° of tem- 

 perature, in order that the effects of different rates of cooling might be 

 observed and the best quality selected. 



The next communication is from INIr. Fairbairn, addressed to His Grace 

 the Duke of Argyll, a member of the Committee, dated Cardross, Perthshire, 

 Sept. 27th, 1853. This letter was submitted by His Grace to the Minister 

 for War, and to the Select Committee at Woolwich. 



Mr. Neilson's communication to the Mechanical Section, " On Forging 

 large Masses of Malleable Iron," proved that the strength and otlier pro- 

 perties of wrought iron are seriously injured by repeated heatings, that there 

 is a considerable loss by oxidation, and that the cost and risk are great. 

 These considerations, and others arising from the physical properties of 

 wrought iron, its ductility and want of elasticity, clearly show that it is not 

 a material adapted for the construction of heavy ordnance. 



We must therefore inquire, what material at our disposal is best calculated 

 to ensure durability and strength for heavy guns. Cast steel is expensive, 

 and hitherto has not been manufactured on a sufficiently large scale to ensure 

 its application. We have therefore to choose between brass gun-metal and 

 cast iron. The latter appears by far the more eligible, both as regards its 

 density and cost, and it opposes almost as much resistance to strain. The 

 failure of recent cast-iron guns arises from the employment of an unsuitable 

 description of that material, and from errors in their manufacture. 



It is our opinion that guns of the very best quality can be manufactured 

 in this country, provided that more care is taken in smelting and casting ; 

 that cold-blast iron, smelted with coke free from sulphur, is used ; and that a 

 proper selection of flux and ore is made. The introduction of the hot blast 

 has given great facilities not only for the reduction of crude ores of inferior 

 quality, but at the same time it enables the manufacturer to melt down cinder 

 heaps and other impurities which cause the iron produced to exhibit all the 

 conditions of porosity and weakness. On this account hot-blast iron should 

 be absolutely prohibited in the manufacture of ordnance ; there is no excuse 

 for ils employment, as we are confidently assured, that several makers are 

 prepared to supply Government with any quantity of the required descrip- 

 tion at a proportionate rate of cost. Careful selection of the material and 

 attention to its treatment are only therefore required to produce iron suitable 

 for guns of any power or strength. 



Being satisfied on these points, we have next to consider how to make 

 use of the material to pioduce guns of a maximum strength. The contrac- 

 tion that a large mass of metal undergoes, in becoming solid, is known to 

 have a very injurious effect on its tenacity and strength. In casting guns, as 

 at present managed, the cooling process proceeds from the exterior to the 

 interior, and the consequence is that the central portion is porous and to a 

 great extent devoid of density and cohesion. It does not require much 

 practical skill to know that the use of a core would remedy this defect; and 



