THE EOYAL ARTILLERY INSTITUTION. 
27 
It was in the first instance necessary to obtain some data upon 
which to work. What limit of resistance should be assigned to 
justify the acceptance of a magazine as “ fire-proof ? ” I thought 
that I could not do better than apply to the Superintendents of 
the Fire Brigades of our chief towns for their opinion as to what 
constituted “ fire-proof/' 1 
Their answers varied considerably, but none of them assigned a 
higher time than six hours. I accordingly took this as the basis, 
and informed Messrs. Milner that their magazines must be capable 
of resisting an intense fire for at least six hours; and in the event 
of other safe makers submitting “ fire-proof magazines ” for trial, 
I am of opinion that this test should be adhered to. 
Messrs. Milner and Co. were also informed that the whole of the 
expense of the trial must be borne by them—a condition which 
they accepted. Under these circumstances, and having obtained 
the permission of the Secretary of State for War to carry out the 
experiments on the Woolwich marshes, the experiments were fixed 
for the 9th October. 
I append the programme which was drawn up for the occasion. 
(Appendix B.) 
It will be observed that it was proposed to test four safes, one 
of them being made more resisting than the others, and being 
designed by Messrs. Milner to resist fire for eight or nine hours. 
Drawings, and a specification showing the construction of the 
magazines designed to resist six hours, are appended. (See 
Appendices 0, D x , D 2 , and D s .) 
The magazine which was designed to resist eight or nine hours, 
differed from the others only in having 6-in. chambers; the door 
being proportionally thickened. 
The whole of the magazines had an internal capacity of 
19 x 14 x 16 ins. = 4256 cubic inches, and were intended to hold 
100 lbs. of powder in canisters. 
The principle of these magazines is that of filling the chambers 
with a vapourising material, such as alum, mixed with a certain 
proportion of non-vapourising, non-conducting material, such as 
sawdust. The original idea was, I believe, to fill the chambers 
with water, closing a number of holes in the interior with fusible 
plugs (of bismuth); when the plugs were fused by the heat, the 
water flowed into the interior, wetting the contents and rendering 
them impervious to heat for a considerable period. 
This arrangement, ingenious as it was, was open to some 
practical objections. For example, the metal of the safes gradually 
deteriorated under the influence of the water, while the freezing of 
the water within the chambers was apt to injure the containing 
case. The present system, which I gather from the reports of a 
trial which took place in the Court of QueeAs Bench,* was ori¬ 
ginally invented and patented by a member of the present firm, 
is a more scientific application of the principle above mentioned. 
As to meaning 
of the expres¬ 
sion (< fire¬ 
proof,” in its 
application to 
a magazine. 
Nature and 
construction of 
magazines sub¬ 
mitted for 
experiment. 
* Milner v. Harrison, 
