78 
POPULAR SCIENCE REVIEW. 
the prolonged part is open for a sufficient length to admit of the intro- 
duction of a cartridge. Upon the prolonged part there is a cap connected 
with a screw-plug, which plug screws in the said prolonged part and closes 
it. A rod passes through a hole in the centre of the said screw-plug, and 
terminates in the prolonged end of the barrel with a conical plug or closer, 
which accurately fits the conical end of the charge- chamber. The rod 
of the plug or closer is made semi-cylindrical, or of a prismatic figure, 
through the greater part of its length, its outer end being cylindrical and 
of small diameter. The hole in the screw-plug, through which the rod of 
the closer works, is of the same figure as that part of the rod which passes 
through it. The projecting end of the rod is provided with a button or 
knob, by which the said rod can be pushed forward and withdrawn. 
Where the rod is pushed home, and the plug or closer made to close the 
end of the barrel, the screw-plug is turned by means of a handle attached 
to it, and the hole in the said screw-plug is made to cross the end of the 
rod, and a shoulder on the said rod is thereby supported by the screw- 
plug, and the plug or closer firmly fixed to its seat. The firearm is then 
ready for discharge. To recharge the firearm after firing, the screw-plug 
is turned a semi-rotation, so as to bring the opening in the screw-plug 
coincident with the rod of the closer. The closer can now be withdrawn 
from the breech-chamber and a fresh cartridge introduced. 
Powder-Flasks. — Mr. G. Hay craft, patentee. — These flasks the patentee 
makes with a hollow cylindrical screw stopper, and with a screw-thread 
formed upon the outer side of it. This hollow cylindrical stopper closes the 
mouth of the flask, there being a corresponding female screw formed in the 
neck thereof ; the stopper is closed at the other end by a head-piece ; it 
serves, when the flask is open, as a measure for the powder, it being made 
to contain one charge thereof. 
Propelling Vessels. — Mr. A. Johnston, patentee . — This invention 
relates to a method of propelling vessels by means of an improved pro- 
peller, consisting of one or more pairs of submerged cylinders, fitted with 
pistons of the form hereinafter described. The patentee makes use of one 
or more pairs of these cylinders and their pistons, and he places them, 
water-tight, below the light-load water-line in the stern or other suitable 
part of the ship. The cylinders and their pistons are used in pairs, each 
pair of pistons by the piston-rods being connected to each other by means 
of a rocking-beam or beams placed inside the ship. By reason of being 
connected to this rocking-beam the pistons are balanced and kept in their 
relative positions. The propelling pistons (which he calls the water-pistons, 
to distinguish them from the steam-pistons) are formed with projections 
or noses, which extend from the piston-head and packing of the water- 
pistons towards the mouth or open end of the water-cylinders. These 
projections or noses must be made of a size sufficient to fill up the whole 
area of the water-cylinders when the pistons are drawn back, leaving 
just space enough to avoid friction or rubbing against the inner surfaces 
of the said water-cylinders, and the ends of the projections should be 
slightly dished or hollowed out, so as to enable them to take a better hold 
of the water. The projections may be made of cast-iron, and should be 
made hollow, but they must be made of such weight as to be equal or 
