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104 
fication pierced with its embrasures. All varieties of mate- 
rials were employed in the walls, and every suggested 
method of constructing the embrasure was tried. Gene 
Totten’s report shows that the minutest detail of construc- 
tion was directed by himself, and that he personally super- 
intended the experiments. They were carried on at inter- 
vals during four successive years, the results of each year 
suggesting the object of experiment for the next. 
It would be out of place here to follow the report through 
its detailed accounts of the firings, or even to attempt to 
sum up the conclusions arrived at, referring as they do to 
such a variety of subjects; but those concerning the thick- 
ness of the scarp-wall and the use of wrought-iron may be 
properly quoted as among the most important. 
“The general conclusion from these trials is, that, whether 
of cement concrete, of bricks, or of hard stones, the portion of 
the wall at and around each embrasure having the thickness 
of five feet only should be no larger than is indispensable 
for the adaptation of the gun and carriage to the embrasure; 
if restricted to a small area, this thickness will suffice, — 
not otherwise. 5; 
“The thickness of five feet will resist a number of these 
balls, impinging in succession on that space, provided the 
bond expand promptly above, below, and on each side, into a 
thickness greater by some two and a half feet or three feet 
or more. Were the wall no thicker generally than five feet, 
being reinforced only by piers some fifteen feet apart, it 
would soon be seriously damaged by battering at short dis- 
tances.” 
And in reference to iron it is stated: “ First, It may be 
fairly assumed, that a plate eight inches thick of wrought 
iron of good quality, kept in place by a backing of three 
feet of strong masonry, will stop a solid ball from an eight- 
