103 
of his determinations, which neglected no appreciable mag- 
nitude, and the thoroughness and generality of his solu- 
tions 
8. 
When the embrasure of 1815’ was designed, ships’ arma- 
ments contained no gun heavier than a twenty-four or thirty- 
two pounder. As the calibres increased it became a matter 
of doubt whether the five feet thickness of wall immediately 
about the embrasure was sufficient. At the same time the 
progress made in the art of forging large masses of iron had 
suggested that by its use the funnel form of the mouth 
might be entirely done away with, and the exterior opening 
reduced to an absolute minimum. Nothing but experiment 
could lead to sound conclusions, and the experiments re- 
ferred to on a former page were instituted, the princi- 
pal objects of which were (in General Totten’s own lan- 
guage) :— | 
I. “To ascertain the effects of firing with solid balls, with 
shells, and with grape and canister, from heavy ordnance 
at short distances, upon various materials used in the con- 
struction of casemate embrasures. ; 
II. “To determine whether these embrasures might have 
aform that would shut out most of these missiles, and re- 
Sist for a time the heaviest, without lessening the sector of 
fire, horizontal and vertical, of the casemate gun. 
TIL “To determine the degree to which, without injury 
from the blast of the gun, or lessening its scope of fire, ioe 
throat of the embrasure, and also the exterior opening, 
might -be, lessened. 
IV. “To determine whether all smaller missiles might 
hot be prevented from passing through the throat into the 
battery ; and whether the smoke of the blast might not also 
be excluded by simple and easily managed shutters.” 
Targets were constructed, representing the wall ofa forti- 
