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MINUTES OF PROCEEDINGS OF 
samples. It also accounts for their more than usual dryness; for if the 
powder be porous, the more readily will it part with its moisture. 
The same remark applies to 25. 1.73 samples; for evidently both sets have 
been dried sufficiently, and part of the moisture is to be regarded as what 
the powder has re-absorbed after stoving. The 3. 1. 73 samples being less 
dense, though they have been more dried at first, may, at the time of 
being tested for moisture, have absorbed more moisture than the 25.1. 73 
samples, which are denser. The amount of moisture, however, in powder 
gives very little idea of what may be expected at proof. This had long been 
known, and a very short inspection of the samples already given will show 
that this is the case. The reason of this, however, was now capable of being 
explained; for evidently the powder must dry from the surface to the centre, 
and probably in the centre of each grain there is a considerable portion which 
receives little drying. The average amount of moisture will therefore be 
determined by the amount which was in the powder before stoving, and will 
give but little idea of the amount of dryness of the outer portions of the pebbles, 
which have the most important effects on the proof. 
The 8. 2. 73 samples admit of ready explanation on the same principles. 
Though more pressed, the density is again lower. The grains of charcoal, 
being harder, will still more refuse to incorporate, and will make the powder 
more brittle and less pasty, which will manifest itself in the density at 
pressing. 
The 6. 3. 73 samples show the old tendency to low velocities. Comparing, 
however, these samples with powder made at the same period in 1871 and 
1872, which was dried the same amount, it appears that the densities then 
were less, and consequently the rule still holds good. 
With fine-grain powder, long milling and slack-burned charcoal increase the 
velocity obtained at proof, but with pebble the reverse holds good; and here we 
have an exact parallel to the case of fine-grain and large-grain powder in 
large charges. With fine-grain powder in small charges, the charcoal pro¬ 
bably has not time to seek its oxygen unless it be brought very intimately in 
contact with it; but in large charges, where the time of explosion is neces¬ 
sarily much longer, owing to increased resistance of the shot, time is not so 
much an object, and the great heat may release the oxygen much more 
effectually and rapidly. It is probable also that each small particle of char¬ 
coal may require a certain time to burn, and there may be ample time in 
large charges, but not in small charges unless the particles are pulverised 
considerably by long milling. It is well known that a “ mixed charge ” will 
only just flare up if fired in a small quantity, but if it be fired in bulk the 
result is an explosion. This explains the observation made with regard to 
the Karnes pebble; for if that firm over-milled their powder with the idea of 
getting up the velocity, from what has been said it will be seen that it 
would produce the opposite effect. 
Another observation may be made with regard to the manufacture of 
pebble-powder bearing on the same point. Powder when incorporated in 
the mills usually has a certain per-centage of moisture in the charge with a 
view of aiding the incorporation. Pine-grain powder is usually worked with 
about 3 per cent, of moisture, but pebble with from 3J to 6 per cent. An 
explosion of fine-grain powder with 3 per cent, of moisture is very violent, 
and generally destroys the building; but, with pebble-powder and 5 or 6 per 
