1874.] Engineering. AIL 
Websky has recently analysed the mineral called Strigovite, which occurs in 
granite at Striegan in Silesia. 
A mineral resembling chalcomorphite has been found in limestone enclosed 
in the lavas of Ettringen, near the Lake of Laach, and has been recently 
described by Herr J. Lehmann as Ettringite. 
The extremely rare mineral Osm-iridium, an alloy of osmium and iridium, 
has been discovered in small quantity near Stockyard Creek, Gippsland, in the 
Colony of Victoria. 
Prof. Rammelsberg has communicated to the German Geological Society, 
at Berlin, several new analyses of Idocrase, or Vesuvian, accompanied by a 
review of our knowledge of the chemical composition of this species. 
Some notable examples of the occurrence of crystals of quartz have been 
collected by Dr. Websky, and described in a crystallographic paper published 
in Leonhard and Bronn’s * Jahrbuch.” 
ENGINEERING—CIVIL AND MECHANICAL. 
Guns.—A paper of some importance at the present time, when the size of 
guns is growing so rapidly, was recently read before the Institution of Civil 
Engineers, by Mr. G. W. Rendel, on ‘ Gun-Carriages, and Mechanical 
Appliances for Working Heavy Ordnance.’ Owing to the increase in the 
power and size of ordnance since the introduction of armour, gun-carriages 
have gradually become elaborate machines, and the appliances for working the 
monster ordnance now in contemplation will tax all the resources of mechanical 
science. The first difficulty experienced in mounting the Armstrong rifled 
guns arose from the much greater violence of their recoil as compared with 
that of the old cast-iron guns, a disadvantage mainly resulting from their 
superiority in lightness, strength for strength. After describing a self-acting 
brake for arresting recoil, designed and successfully tried at Elswick in 1864, 
reference was made to the great superiority of wrought-iron over timber as a 
material for gun-carriages, and experiments made in 1865 were cited as showing 
the error of the popular objection entertained against wrought-iron on the score 
of its producing, when struck by shot, more numerous and destru¢tive splinters 
than timber. By the adoption of mechanical arrangements for the application 
of manual power to the working of ordnance, guns up to 25 tons weight can 
now be worked with more ease, safety, and rapidity than guns of a fifth of that 
weight were formerly worked. Guns, however, are now being made of nearly 
double that weight, and hence the adoption of some inanimate power, in the 
place of mere hand labour, for loading and working heavy ordnance, has become 
an absolute necessity for guns of the future. The simplicity and compactness 
of hydraulic machinery, and the perfea control it gives over heavy weights, 
especially adapts it for the purpose. Hydraulic power sufficient for the 
heaviest gun may be transmitted through a very small tube for long distances 
and by intricate ways, so that a steam-pumping engine may be placed in a 
fort or ship in such a position as to be absolutely secure, and supply power by 
this means for working many guns. The arrangements for loading and working 
guns by hydraulic machinery embrace a new system of mounting turret-guns, 
in which the carriage is dispensed with, and the gun is supported on three 
points, viz., on a pair of trunnions placed well forward, and on a saddle under 
the breech itself. The trunnion-arms rest in two sliding-blocks, which run in 
guides on fixed beams, built on the floor of the turret; and immediately behind 
each block, in the direct line of recoil, are two hydraulic cylinders for checking 
recoil and running the gun in or out, whilst the saddle which supports the 
breech slides along a beam or table beneath it. The front of the beam can be 
raised or lowered by a hydraulic press to give any desired elevation, but the 
rear is pivoted at a point corresponding to the horizontal position of the gun; 
consequently it always returns to the horizontal position as it recoils, whatever 
elevation it may be fired with, clearing the port in coming back. Thus the 
advantage of muzzle-pivoting, viz., the reduction of the size of port-holes, is 
