416 REPORT— 186G. 



52-7 tons per inch of shot's cii-cumference, and that thej failed to pass tlirough, 

 although the plate was cracked and opened at tlie back. 



The Special Committee on Ii-on carried out some experiments with a wall- 

 piece, filing steel flat-headed shot at |-inch unbacked plates placed at various 

 angles. 



The waU-picce is able to pierce this plate in an upright position, but it 

 failed to do so in any case when the plate was at an angle. It is a pity this 

 experiment was not continued with diiferent thicknesses of plates, as the 

 present results do not afford sufficient data. 



The results of experiments with this waU-piece have proved that much 

 valuable information may be obtained at a comparatively trifling expense. 



Although it would be of advantage to carry out further experiments on 

 the eifect of fire directed obliquely against iron defences, still we have suffi- 

 cient evidence to prove that the power of resistance is much increased by 

 placing the target at an angle. This result is in favour of turrets or cupolas 

 for sea and land defences, as there is a great probability that such structures 

 wiU be struck obliquelj-. 



It is also in favour of protecting guns by ii'on shields placed at a slope, 

 and not upright. 



The effect of Cast-iron Projectiles as com_pare<l with Steel of the same size 



and form. 



The difference between the effects of cast iron and steel shot is most 

 marked. The latter material is the nearest approach to perfect hardness 

 and cohesion which we have been able to procure, and the amou7it of work 

 expended on the shot is less with steel than any other known material. 

 With ordinary cast iron a very large amount of "work" is expended in 

 breaking up the projectile, and hurling the fragments in all directions. When 

 steel shot are manufactured in the best possible manner, very little " work'' 

 is expended on the projectile; and in one instance a 12- pounder Whitworth 

 steel shot was of such perfect material that, after passing through 2| inches 

 of solid iron, its temperature was apparently imaltered, and its form so slightly 

 changed that it might have been fired from the gun a second time. Several 

 experiments have been instituted with a view of ascertaining the amount of 

 work lost by the breaking up of cast iron, alteratiou of form of steel shot, etc. 



Su- William Armstrong endeavoured to treat the question by an applica- 

 tion of the dynamic theory of heat. Having fired jn-ojectiles of various 

 materials against iron plates, he attempted to measure the quantity of heat 

 generated by the concussion. 



This method was verj- ingenious, but most difficult to carry out ; and the 

 results of such trials can only be looked upon as approximate. 



The conclusions drawn by Sir William Armstrong from his experiments 

 were as follows : — 



1st. With hard and well-tempered steel shot the " work " expended on 

 the projectile was about one-tenth of the total work in the shot on impact. 



2nd. With soft steel the "work" expended on the projectile was about 

 two-tenths of the whole " work."' 



3rd. With soft wrought iron it amounted to nearly one-half. 



These experiments are alluded to in the memorandum on this subject by 

 Professor Pole, F.R.S., published in the Report of the Special Committee 

 on Iron, 1862, p. 30. 



If we examine the results of the various experiments in which cast-iron pro- 

 jectiles were used in comparison with, or under the same circumstances as, steel 



