58 Modern Cannon Powder. _ [January, 
believed that these can now be made of accuracy sufficient 
for this purpose. 
Great care would be required in taking the photograph of 
the fine equidistant lines, to secure their being accurately in 
focus; but the true focus once found and fixed, the photo- 
graphs might be multiplied indefinitely, at a moderate cost. 
These hints are merely thrown out for the consideration 
of practical opticians, and it is quite possible that there 
may be graver difficulties which have been overlooked. 
Nevertheless, the devising of some means for constructing 
a spectroscope on the diffracting principle is well worth the 
consideration of those engaged in the manufa¢ture of this 
instrument; for until this principle be adopted, accuracy, 
certainty, and uniformity of results, cannot be attained. 
VI. MODERN CANNON POWDER. 
es 
he the year 1779, nearly a century ago, General 
sl Sir William (then Captain) Congreve was sent to 
Plymouth to examine the gunpowder with which the 
Fleet was then supplied, on which occasion he reported that 
there were only four barrels of serviceable powder in the 
whole of His Majesty’s ships. This state of affairs was no 
doubt due to the fact that the country was then entirely 
dependent on private manufacturers for its supply of 
powder, and that the proof to which it was subjected was 
not such as to ensure its being of good quality. On discovery 
of the gross frauds which were thus being carried on with 
impunity, the Government Gunpowder Factory at Waltham 
Abbey was established, and, under the able superintendence 
of Sir W. Congreve, the quality of the powder supplied to 
the army and navy was greatly improved. 
From this date until the general introduction of rifled 
guns in 1860, very little progress was made towards the de- 
velopment of this important manufacture, the only changes 
being in the direction of improvements in the preparation 
and purification of the ingredients, the quality of the finished 
powder being thereby improved, while its character remained 
unaltered. During the whole of this period the description 
of powder used with all cannon was what is technically 
called ‘‘ L.G.,” or “‘ Large Grain,” in contradistin¢ction to 
‘““E.G.,” or “ Fine Grain,” which was used with small arms 
and muskets; but this powder was believed to be too violent 
