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safety so notorious in the case of our iron-bound guns, in which the 
expansion of the outer layers of wrought-iron is considerable after the 
limit of elasticity is past. 
Should the adjustment mentioned not always be perfect, as is pro¬ 
bably the case, considering manufacturing difficulties, and the varying 
nature of steel, we have an unpleasant doubt as to the safety of a Krupp 
gun exposed to any excessive strain. 
4.—“ The scoring of the barrel is a purely mechanical work in which 
chemical action plays no part. Experience shows that brittle metals, 
or hard places in bronze guns, are most liable to scoring. The vent 
must consequently be made of the softest copper. 
Just as the sand blast* spares soft and attacks hard substances, so 
the powder-gas in a high state of tension and mixed with uncon¬ 
sumed powder, escaping by a narrow opening, eats first into the 
hardest spots it encounters. This accounted always for the proneness 
to scoring of the old bronze guns.-j- The new guns will have no tin 
spots, and the metal is not brittle; they will not, therefore, be more 
liable to scoring than steel guns. 
Remarks .—“ We can only answer that in the first place, the General 
has not yet succeeded in casting the metal without tin spots, while, if 
his theory is correct, that f hard places in bronze guns are more liable 
scoring/ it follows that the bronze steel gun must be more liable to 
this defect than a gun of ordinary and well-cast bronze, since the 
former metal is much harder."” 
As to this condition his critic seem to have the best of the argument, 
for General Yon Echatius indulges in prophecy when he states, that 
his new guns will have no tin spots. 
As to the other point, he may perhaps maintain, that some of the old 
tin spots containing “ putty powder,” were even harder thanbronze steel, 
while he can scarcely be wrong in stating, that “ they will not be more 
liable to scoring than steel guns.” 
Upon the wide question of the physical properties of metals, his 
critic is rather hard upon General Yon Uchatius, stating that he 
“ arrives at the extraordinary conclusion that the tougher metals attain 
their maximum capabilities when strained beyond their limits of 
elasticity, i.e. } when permanently extended.” Also further on, (< he is 
working upon a false conception of elasticity and strength,” i.e ., in 
maintaining that a bar so strained attains an “ increased tenacity.” 
All this seems based upon a mistake as to the terms used. For 
General Yon Uchatius does not appear to imply that the total strength 
of a metal is so increased, but only that its breaking strain is increased, 
and that bronze thus treated attain its maximum capability for his 
* This refers to an American invention in which a strong blast of air, or steam carrying 
sand with it, is directed npon a sheet of glass which has previously been coated with some 
yielding substance, except where it is desired to cut a pattern—the hard uncovered 
portions are quickly eaten away by the sand driven against them while the yielding 
surface remain uninjured. 
f The tin spots though more readily acted on by heat, are harder than bronze* 
