SCIENTIFIC SUMMARY. 
95 
rated by the explosion of the powder, a pressure wbicb may reach 60,000 lbs. 
per sq. in. This can be modified to some extent by the use of large grain 
or pebble powder, which burns more slowly than powder of finer grain. 
Mr. Bessemer, however, proposes to secure any required reduction of the 
initial pressure in another way. Instead of having a single large charge of 
powder, he proposes to have a series of 20 to 100 smaller charges, ignited 
successively as the shot travels along the bore of the gun. But this suc- 
sessive ignition of the powder would be less efficient than the explosion of 
a single charge in propelling the shot, unless means were taken to keep the 
shot under the action of the powder-gas for a longer period than in an 
ordinary gun. Hence Mr. Bessemer proposes to increase the length of the 
gun to 50 feet. By these two changes, Mr. Bessemer is said to hope to 
propel shot, the weight of which may be measured by tons, not by pounds. 
Mr. Bessemer’s gun, illustrated in “ Engineering,” September 15, consists of 
inner tubes of welded wrought-iron, strengthened by steel rings, shrunk on 
with suitable initial tension. The gun is made in lengths, connected by 
flanges. The cartridge-chamber is chambered, and the charges may be 
successively ignited by fusees, or by means of electricity. Further, Mr. 
Bessemer suggests that rotation may be given to an elongated shot, not by 
rifling, but by the reaction of jets of powder-gas issuing from tangential 
orifices at its circumference. The powder-gas is supplied by a charge of 
powder burning in its interior, and the rotation is caused by the reaction of 
the jets, on the same principle as the rotation of Barker’s mill or the Scotch 
turbine. 
Wood-engraving by Machinery. — A process for engraving on wood by the 
cutting action of a sand-blast, is described in the “ Journal of the Franklin 
Institute.” A photographic copy of the drawing or object to be engraved is 
formed on a suitable matrix. This is then acted upon by a jet of sand, the 
particles of which have a very high velocity, so as to cut away to varying 
depths the surface of the block. The block is then electrotyped, and the 
engraving is printed from the electrotype. For various cutting and polish- 
ing purposes, the sand-jet seems likely to prove extremely valuable. 
Gunpowder Gauges. — M. le Commandant de Beffye has used a form of 
gauge for determining the pressure in the bore of large guns, the principle 
of which has been suggested by M. Tresca’s experiments on the flow of solid 
bodies. A block of lead is placed in a cylindrical hole bored into the gun, 
and is supported behind by a steel block through which a smaller cylindrical 
hole is bored. When the pressure acts on the lead, it forces it in part into 
the cylindrical cavity behind, and the volume of lead thus forced in forms 
a measure of the pressure in the bore of the gun. 
St. Gothard Railway. — It is said that the St. Gothard Bailway, with a 
tunnel about as long as the Mont Cenis tunnel, will be commenced very 
soon, and that the Mont Cenis staff will be transferred to undertake its con- 
struction. 
Flow of Liquids. — Canon Mosely in the “ Philosophical Magazine,” and 
Professor Colding in the “Copenhagen Transactions,” have been investi- 
gating the laws of the motion of water in pipes, conduits, &c. The gene- 
rally accepted formulae are known to be defective. They are founded on 
the assumption that the water moves in plane layers at uniform velocity. 
