THE ROFAL ARTILLERY INSTITUTION. 
89 
8-in. gun was satisfactory, it was imagined no further difficulty would be 
experienced. 
The method at first adopted of breaking up the press-cake into pebbles was 
the same as that described for producing the 2A 4 grains—viz., the use of 
copper hammers. This is manifestly a very tedious and troublesome process. 
It is still, however, to be seen in operation at the Wetteren Factory, in 
Belgium, where the cake is first cut into strips by a sort of guillotine machine, 
and afterwards broken up in this fashion, by means of wooden mallets in a 
hollow hemispherical bowl, into pebbles. 
A system of chopping up the cake by means of copper knives very soon 
superseded the method of breaking up by hammers at Waltham Abbey. The 
cake was first cut up into strips by the knives, and these strips were again 
chopped across into pebbles by the same instrument. It was, of course, a 
tedious process, but it had the advantage of making little or no waste, and 
nearly the whole of the press-cake could thus be converted into grain. 
A good many experiments were tried with a view to granulate the pebbles 
in the same way as ordinary powders, but all the attempts were very 
unpromising,, owing to the irregularity of the grains and the great amount of 
waste. Messrs. Curtis and Harvey, however, produced a large proportion 
of their pebble-powder supplied by contract in this manner. They only, 
however, obtain about 30 per cent, of grain from their cake; and though 
this low per-centage does not inconvenience them, inasmuch as they can 
find other uses for the smaller grains, it would not be sufficient in a 
Government factory, where there is no other use to which they could be 
applied. 
The chopping-knife was in operation for a considerable time, and turned 
out the whole of the pebble manufactured at Waltham Abbey from August 
1870 to May 1871, during which time about 4000 barrels of 125 lbs, each 
were manufactured and sent to Purfieet. 
The following woodcut will serve to give an idea of the nature of these 
instruments:—- 
Fig. 1. Scaled 
