Daily national Republican. [volume] (Washington, D.C.) 1862-1866, 1863-01-24
LOCAL NEWS.

LEoruRE AT THE SMITHSONIAN Hors.
ford, Of Harvard University, lectured last ever
ing on the munitions OF war. The dense au-
dience present listened with marked attention.
a great many attempts, he said, had been made
~ various times to form gunpowder OF tho ro-
quirod strength. Tho proportions we employ,
as also do tho French, consist Of 100 parts Of
saltpetro and 10 each of sulphur and charcoal.
The powder used In Prussia, Austria and else
where varies considerably from this standard.
He gave minute description Of the progress
IN constructing cannon, from tho earliest
periods Of lis use 10 tho present time. They
werofirst made Of wrought iron, but these fell
into dlsuse In the latter part Of the fifteenth
century, in fact, there was a royal odict for
that purpose. Then appeared guns OF Cast-lrou
and hronEs, one Of the largest and finest specl.
mems Of which was the immense bronze gun
mounted on the -Kremlln in Moscow, which
consumes vast amount Of powder In It's dis.
charge. There arc also great numbers of this
sort OF gun az tho present day, ranged along
the Dardanclles. About D century ago, some
Frenchman attempted 10 revive the wrought
iron guns. But this was by no means the only
specimen yet extant for when the Tachu forts
In China were captured, several wrought iron
guns were found in them.
With few such exceptions, no experiments
for this result were made until about twenty
hve years ago, when Prof. Treadwoll, in this
country, constructed gun free from most OF
the defects which had drst caused the abandon.
ment ofthis style of cannon. Sir VIM. Arm
strong's model, however, evlnccd a still further
improvement in the choice aud disposition OF
the metals The Whltworth gun, In many re-
spects, differed entirely from the Armstrong.
II was forged from steel, the most expensive
material that could be used. The Longridge
gun, In England, lie another Of the wrought
] on class We come now to consider east Iron
guns, They are made by tho following pro.
cess; wooden model Is first thrust Into the
sand, and into the cavity thus formed the
motion metal ls poured, and gradually COols.
The upper portion Of the gun iS then cut of as
containing the impurities which rise 10 tho sur.
face, and becoming thereby porous. The dis.
advantage Of such process Is that the outside
OF the cannon, radiating Its heat first, must
shrink, and cause the production of holloNs OF
pores In the interior.
To remedy this difficulty, Captain ROdmau
tried to make this shrlnkagc, the means only
to Increase the strength of the cannon. His
plan was 10 cast the gun hollow, and cool the
Interior by constant stream Of water; and Ia
prevent the outside from cooling, he built q
hrc around IL. In this way the surface In con.
tact with the water first hardened, and the
metal gradually grew lees compact as 1t ap,
preached the exterior. The great gun at Fort
ress Monroe was constructed on this model
In all these guns the centre Of gravity was In
the trunions, for which reason they could bt
managed with much ease. Captain Dahlgrer
proposed to abolish the trunlons, and invent
some other Contrlvance TO answer their PURPOSE
without the risk Of causing shrnkage, as wal
the case with them. He also carried the masi
Of metal, principally towards the breach, around
which the greatest tension was exercised.
Tho combination Of the wrought-iron will
cast-iron and bronze produced another order Of
cannon. Prof. Treadwell's gun, submitted t.
the Government in 1915, WIS of this pattern
also, Capt. Blakely's gun, In England, and Mr.
Parrots, formed at the breaking out of oul
civil war. The great end to be attained In gun
merry Is to find out the exact amount Of pressure
exerted on the particles of the iron In firing ord
nance. Capt. Rodman, for this purpose, borcc
variety of holes In the sides Of the cannon
which were stopped, and an instrument was in
serted which showed at every discharge the forct
OF the powder on each Of these small apCrturos