ss 
MINUTES OE PROCEEDINGS OE 
that extensive and systematic experiments should be carried out with the 
latter powder. They also tried experiments with a pebble-powder which then 
went by the name of 2A 4 . It was made at Waltham Abbey, in imitation 
of the American mammoth powder, by breaking up press-cake with copper 
hammers, and sifting the pieces between meshes of 1 and 2 to the inch. The 
effect of density in modifying the action of powder was overlooked, and this 
powder when fired in the B.L. guns was found not only to destroy the vent- 
pieces, but also to enlarge the chambers of the guns—the latter circumstance 
showing that the fault lay not in the guns but in the gunpowder. It differed 
from the American mammoth in one very important respect, being only 1*62 
instead of 1*82—which is the American density for both cannon and mammoth 
powders. It is unfortunate that further experiments were not tried with 
higher densities, as it is probable that thus we should have had our pebble- 
powder much sooner than has been the case. The importance of density, 
however, was not at that time so well understood as it now is, and there 
appears to have been a bias on the minds of some of the members of the 
Committee in favour of regular grains pressed separately in moulds, which 
process they considered also could be carried on more economically than the 
granulation of 2A 4 powder, where there was a great amount of waste. 
The introduction of the mercurial densimeter at a later period allowed 
the question of density to be more satisfactorily dealt with. This instrument 
was first designed in Trance, and was used for some time in the Chemical 
Department, Eoyal Arsenal, before it was introduced into the Royal Gun¬ 
powder Factory at Waltham Abbey in 1869. 
The present Committee on Explosives, under the presidency of Colonel 
Youngliusband, Superintendent Eoyal Gunpowder Factory, Waltham Abbey, 
was appointed in 1869, and conducted an extensive series of experiments with 
various powders by methods similar to those used by Eodman, which led 
them to the conclusion that pebble-powder was better suited to the require¬ 
ments of the service than pellet-powder. As it is also now very much easier 
and safer to manufacture, the change they recommended from pellet to pebble 
is not to be regretted. It is the slow and steady progress in the manufacture 
of this powder that forms the subject of this paper, and which will best be 
explained by giving a short historical sketch of the process as carried out at 
Waltham Abbey, and by those merchants who have supplied pebble-powder 
under contract. Dependence may be placed upon the facts adduced ; but it 
will be well to be cautious in accepting too readily the conclusions drawn, 
because there is no subject where hasty conclusions are so apt to be over¬ 
thrown as is the case with the manufacture of pebble-powder. 
The first specification sealed to govern the manufacture was 16. 5. 70, the 
density being 1*8, the size of grain between f and \ in., and when fired in 
the 8-in. gun the velocily between 1420 and 1480 f.s., and the pressure in no 
case to exceed 20 tons in the bore of the gun, as indicated by the “ crusher ” 
gauges in use by the Committee. Soon afterwards, however, it was found 
there was a difficulty in maintaining the velocity, and the specification was 
altered as regards density, with a view to meet the requirements of the case, 
being lowered to 1*765 in August the same year. Some powder had been 
made having a density of 1*8, but it was kept in reserve, and afterwards 
mixed with pebble having a lower.density, so as to give a mean of 1*765. 
The manufacture was continued at this density, and as the proof in the 
