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NOTES ON AKMOURED DEFENCES. 
A Lecture delivered at the It.A. Institution, on 29th April, 1880, 
BY 
COLONEL INGLIS, R.E. 
Long before tbe general adoption of rifled cannon by fleets and 
armies, it was a well recognized fact tbat tbe materials tben in use for armour 
works of fortification were not a match for tbe guns which ships could 
carry. 
Accordingly, we find that early in this century experiments were 
made with iron-cased walls, at Woolwich, not to mention others made 
in much more remote times. 
In 1853, extensive trials were made in the United States with smooth¬ 
bore guns against masonry structures, having in them embrasures 
strengthened with iron and other materials. 
In 1855, the French employed three iron-cased floating batteries in 
the allied attack upon Kinburn, and, before peace was made with 
Russia, England also had iron-clad batteries afloat. 
In 1856, iron plates were tried, both in this country and in France, 
against smooth-bore guns, and, in 1859, a shield for an embrasure, 
composed of massive iron bars, was tested at Portsmouth for Sir J. 
Burgoyne, by the fire of 68-pr. service guns; and besides many other 
trials of smooth-bores against iron about that time, in 1858, two 
armoured floating batteries were experimented upon at Portsmouth, 
by 32-prs. and 68-prs. 
The fact is, that it was nothing but the vagueness of the fire, and 
the rapid loss of velocity in the projectiles, of smooth-bore guns, that 
allowed our works and ships to escape as well as they did in former 
times. And this applies at least as much to other countries as to 
ourselves. 
In this view, therefore, it is not surprising that, when guns of good 
range and precision came to be introduced, some great change in the 
mode of defence should have been commenced. 
But it has been urged that the mere fact of the old walls of our 
works having been found insufficient for the altered fire of artillery 
should not have condemned the material of which they were composed. 
If walls of 5 ft. or 10 ft. thickness were not strong enough, let them be 
made 20 or 30 ft. thick, or more if necessary; and if masonry will 
not do, use more earth or concrete, or something else in large quantities. 
Well, to a great extent, this is really what has been done generally 
in works of fortification; but in forts for coast and river defence* 
which are the only works liable to the fire of the heaviest ordnance, 
and with which alone I have to deal on this occasion, a large addition 
of mass is altogether impracticable. 
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