368 
DYNAMITE. 
As it is, the block of wrought iron here deposited will bear testimony to its great 
power. It was originally a cylinder of 11 in. diameter and 12 in. height, of best scrap 
iron, and cut off from a shaft. The borehole through its centre was exactly 1 in., and 
the charge of 6 ounces was put in without securing either end by any sort of plug or 
tamping. The cylinder was blown at Merstham, on the 14th July, in the presence of a 
large audience. Allowing for the hole, and putting the tensile strength of the iron at 
20 tons per square inch, the strain necessary to effect the rupture must have been equal 
to 2400 tons; and since there was no plug at either end of the hole, it is evident that 
the charge was too much for the work. Besides blasting the cylinder, it had hurled the 
one half here deposited with such violence against a f in. boiler plate at some distance 
as to break it. 
No wonder that a substance which tells so well on iron should be effective against 
rock. 
Coupled with this great power is a safety, for proofs of which I will simply refer to the 
tests publicly made both at Glasgow and Merstham. A box, containing about 8 lb. of 
ynamite (equal in power to 80 lb. of gunpowder), was placed over a fire, where it 
slowly burned away ; and another box, with the same quantity, was hurled from a 
height of more than 60 ft. on the rock below, no explosion ensuing from the concussion 
sustained. 
It is difficult to see what more can be required from a blasting material in order to be 
called safe; but some experiments made lately at Stockholm have put it to a still 
more severe test. A weight of 200 lb. was dropped from a height of 20 ft. on a box con¬ 
taining dynamite, which it smashed, of course, yet no explosion took place. An account 
of this experiment is to be found in the Stockholm paper ‘ Aftonbladet,’ of the 7th of 
this month. 
Such a test can leave no doubt that dynamite offers sufficient safety against concus¬ 
sion for all practical purposes ; and we may say, as a Prussian military commission 
recently reported, that it appears to be the safest of all known explosives. 
To those not fully acquainted with the nature of nitro-glycerine, it seems puzzling 
that a mere absorption should be sufficient to produce such a radical change in its 
essential properties; but when we come to examine the matter closely it is easily 
accounted for. 
The greatest, and almost the only drawback on nitro-glycerine is its liquid form. 
Much as has been written on the danger of congealed nitro-glycerine, I can confidently 
assert that if the solid form was its natural state at the ordinary temperature, we should 
hardly have had to deplore a single one of those fatal accidents which it has caused. 
Moreover, it is a very erroneous notion that crystallized nitro-glycerine is more sensitive 
to concussion than the liquid one. The reverse is the case, and in a very remarkable 
degree; but that is immaterial to the present question, and I only mention it to show 
how fancy notions take root, and defy even the plain truth of simple investigation. 
Nearly all the calamities caused by nitro-glycerine have, in my opinion, been owing 
to leakage, which, for practical reasons, it is very difficult to prevent, and are, therefore, 
indirectly chargeable to its liquid state. A substance sensitive to concussion, unless it 
is quite unmanageable like chloride of nitrogen, can easily be protected against acci¬ 
dents by wrapping it in a soft material ; but if that substance is a liquid and a leakage 
takes place, it becomes subject to the danger of direct percussion ; and if nitro-glycerine 
in that condition becomes exposed to the sun’s rays, the heat which it takes up renders 
it so sensitive as to become dangerous under the slightest blow. 
From the very first beginning I have given special attention to the packing of nitro¬ 
glycerine ; but, much to my regret, I must say that it is as yet far from satisfactory. 
Casks are not tight enough for oily liquids, and the property of nitro-glycerine to expand 
when it congeals has obliged me to resort to square tins. These are left unpacked in 
the factory for a month at least, to ascertain whether they are tight, yet I can scarcely 
remember a single instance of a cart or cargo of nitro-glycerine having reached its des¬ 
tination without a case or more of leakage. The reason is probably to be found in the 
pressure to which the tin becomes exposed when the air which is confined inside, as well 
as the nitro-glycerine, becomes expanded by an increase of the external temperature. 
Whatever be the cause, it is certainly wrong to lay the blame on nitro-glycerine for 
what has been due only to a practical difficulty. Let us suppose, for instance, the case 
of gunpowder being transported in cases dropping out, continuously, part of the contents. 
