1872.] Engineering. 391 
gravity of each species are registered in these tables. In calculating the for- 
mule, the new atomic weights have been employed, and the quantivalence of 
the elements marked in most cases. Many of the formule are constructed, 
however, upon an original plan proposed by Dr. Reynolds some time ago, and 
described in the ‘‘ Philosophical Magazine.” ‘The tables are preceded by an 
explanatory introduction, indicating the system adopted in the arrangement of 
the collection, and containing notes on the more interesting species in each 
group. 
The third part of Dr. Schrauf’s great work—the ‘ Atlas der Krystall-Formen 
des Mineralreiches ’—has lately been published. This part contains ten plates 
comprising 160 finely-executed figures of crystals. The species are arranged 
in alphabetical order, and the crystals figured in the present part extend from 
“* Apophyllite”’ to ‘“‘ Barytes.” 
ENGINEERING—CIVIL AND MECHANICAL. 
Guns.—We have, on former occasions, recorded the history of the celebrated 
‘Woolwich Infant,” as the first 35-ton gun was named. This gun has, since 
the completion of its proof, remained inactive in front of the butts, not having 
fired a shot since the trial was made which proved the non-importance of the 
injury done to its steel lining. Nine other similar guns, completed at the 
Royal Gun Factories, have since been tested, their proof consisting of three 
rounds only, viz., two with the ordinary service charge of 110 lbs., and one 
with the proof charge of 115 lbs. of gunpowder—a more severe strain than they 
are ever likely to have to endure again. 
On the 23rd of March last a paper was read before the Institution of Civil 
Engineers by Mr. Bashley Britten, ‘On the Construction of Heavy Artillery, 
with Reference to Economy of the Mechanical Forces Engaged,’ wherein it 
was remarked that so long as nothing definite was known as to the power 
exerted by gunpowder, the strongest guns were deemed the best. But a good 
gun was a scientific instrument, which like any other engine, ought to produce 
the greatest results with the highest economy of means. -When the principle 
of the rifle was applied to cannon, and elongated projectiles were introduced, 
the skill of engineers soon conquered the difficulty of producing ordnance 
of ample power to resist high bursting pressure; but this success in the 
manufacture of strong guns led to the disregard of other considerations of even 
greater importance, chief amongst which was the use of the strongest powder, 
which after from 500 to 600 rounds destroyed the interior of the guns by the 
intense heat and the pressure of the gases. This led to the appointment, in 
May, 1869, of the Committee on Explosives. From their report, printed in 
1870, the following argument was founded. The Woolwich heavy guns were 
designed for R.L.G. powder, and with it were found to be strong enough 
to bear all the marginal proofs. The 8-inch guns had to bear a pressure of 
from 25 to 30 tons per square inch, and the 1o-inch guns from 45 to 50 tons per 
square inch, from the service charges; but henceforth, with pebble powder, 
the pressure would never exceed about 15 tons in the former and 20 tons in the 
latter case, as no benefit would be derived from a higher pressure. The prin- 
ciples represented in the designs of the Woolwich system of ordnance were 
examined under the following heads, viz.:—(1) the quality of the material 
used ; and (2) the power of the charge; and it was argued that with the use of 
pebble-powder cast-iron might be used with perfe& propriety for the exterior 
of ordnance, at a saving of at least 50 per cent of the cost of the new guns 
even of the present type. A comparison was then entered into with reference 
to the proportion which the bore should bear to the length of the gun, small 
bores and long chases being preferred on account of the greater amount of 
expansion that would be utilised from the explosion of the powder charge 
under such conditions. 
On the 17th of May last Commander W. Dawson, R.N., read a paper before 
a meeting of the officers of the two services, at Portsmouth Dockyard, upon 
the “Seven-Inch Gun.” This paper related exclusively to the system of 
rifling adopted in the manufacture of ordnance at the present day. After 
