THE ROYAL ARTILLERY INSTITUTION. 
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one brick pier 6 ft. thick, but as he fires his guns only five times an hour, his 
estimate of resistance seems considerably too high. The disadvantages of a 
mask of this kind are that it prevents the guns in the casemate from at all 
opposing the construction of the counter or breaching batteries on the crest 
of the glacis, and that very soon after breaching commences it must, unless 
the excavations under its arches are made of a very considerable depth, and 
the expense of its construction thereby much increased, begin to mask the 
fire of the embrasures on the bottom of the ditch. The most practical way 
therefore of protecting the front walls of flanking casemates seems to be to 
construct them of iron. Recent experiments have, I believe, shewn that the 
distance between the piers at the front of the casemate may be reduced from 
12 to 10 ft. and yet allow of the working of a heavy gun; and the question 
at present under consideration is how most economically and efficiently to 
close an opening of this width, and perhaps cover the front ends of the piers. 
I understand that the system of iron planking and cross planking as recom¬ 
mended by Captain Inglis is likely to prove most easy of application, and 
most efficient. 
As to the terreplein of works it will be necessary to provide an ampler 
supply of traverses than formerly, and to increase the distance between the 
guns, so that the merlons may oppose more resistance to the explosion of 
shells.* In any faces or flanks which cannot by their trace be secured from 
enfilade or reverse fire, blindages of a permanent character, such as haxo- 
casemates, must be employed. Though considerably more space than of old 
will thus be required, there can be no doubt a few guns well secured are 
superior to a larger number more exposed. If the fronts of haxo-casemates 
are exposed to fire, an iron protection would be necessary to the masonry, 
and also to the throats of embrasures. The cheeks of earthen embrasures 
will of course offer but feeble resistance to the accurate fire of rifled guns; 
iron shields should therefore be secured to the parapet extending a few feet to 
either side of the embrasure. A practical mode of doing this is pointed out 
by Captain Inglis in the last volume (XI) of the " R.E. Professional Papers.” 
Another method of securing guns on ramparts is indicated by Lieut. 
Duncan, R.A., who proposes, in a paper lately issued in the "Proceedings” of 
this Institution, using for the purpose Captain Coles 5 cupolas. These might 
no doubt be employed with advantage at important points where great lateral 
range is required, such as salients, but they would be too costly for anything 
like general use; and one of the advantages claimed for them, that of doing 
away with the necessity of outworks, can hardly be conceded, since one of 
the main uses of the latter is to bring a reverse and flanking fire on a 
besieger who should be hardy enough to attempt the main work before 
taking the outworks in front of it. Captain Inglis also, in the paper before 
alluded to, advocates the use of revolving wrouglit-iron screens for guns in 
salients. 
With regard to the employment of iron in escarps, the enormous 
expense (calculated by Captain Inglis at about £4 to £5 per foot super), 
would of course prevent the idea being entertained of ever using it largely 
for such a purpose. The plating of any small portion of an escarp, such as 
* As much, as 37 ft. Is allowed in some of the new works. 
[VOL. III.] 
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