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POPULAR SCIENCE REVIEW. 
100, the curves are not less than 200 yards radius, and extreme care 
has been taken in the arrangement of the signals to prevent accidents. 
Trains are to be run at five-minute intervals, and the resources of the 
line have already been taxed to the utmost to convey the passengers, 
over the short distance of 3| miles at present open. The locomotives 
are peculiar in having a condenser, and means of preventing the escape 
of the products of combustion whilst within the tunnels. 
Pneumatic Despatch Company . — A short length of tube has been laid by 
this company, and is in successful operation. It is a revival, on an un- 
objectionable plan, of the atmospheric system of traction tried in thiscountry 
and Ireland and ultimately abandoned. Formerly, as the train on the out- 
side of the tube was actuated by a piston within it, a joint running the 
whole length of the tube was necessary, and the leakage from the latter 
was the most serious defect of the system. In the new plan the train is 
within the tube, itself forming the piston against which the pneumatic 
pressure acts. Thus the joint is dispensed with, and the area subject to 
pressure being much greater in proportion to the weight of the train, a less 
pressure suffices, and the loss from other sources of leakage is correspond- 
ingly reduced. The compression or exhaustion of the air, as the case may 
be, is produced by a large centrifugal fan, which, if constructed on correct 
principles, will be more effective and less costly than the old plan of blowing- 
cylinders. Some passengers have been sent through the small tube already 
laid down, and there is no reason why another, say 9 or 10 feet in diameter, 
should not be employed expressly for passenger traffic. Indeed, the im- 
possibility of collision or explosion, and the absence of smoke and steam, 
would seem to point to this as a safer, healthier, and more economical 
system for the underground railways of London than that adopted by the 
Metropolitan Company. 
Armour Plates and Iron-clad Vessels . — Renewed trial has been made at 
Portsmouth of the laminated system of armour-plating, one modification 
of which is in so much favour in America. In this experiment, planks of 
iron 2|- inches thick were attached in two layers, crossed at right angles, 
so as to be equivalent in weight to 5 inches of solid plate. As in all 
previous experiments in this country, they proved inferior in resistance to 
solid armour-plate. Two bent plates were tested, with a view* to ascertain 
the relative advantages of the hot and cold bending processes, and the 
extent to which they each injured the material. Both plates broke up in 
a most extraordinary manner, and led to serious doubts of the invulnera- 
bility of the curved portions of our iron-clads. A subsequent experiment, 
however, exhibited a different result, and further investigation is necessary. 
Steel plates have again proved failures under trial. In France, armour- 
plates have been pierced by flat-fronted shells, as had been accomplished 
previously in this country ; the weight of the shells 100 lb., charge 
28 lb. to 33 lb., gun of the kind known in this country as the “ Blakeley.” 
Tubular iron tripod masts, and iron chain and wire rope, are likely to 
supplant timber and hemp in mail-clad vessels. They are less subject to 
damage from shot, less obstructive to the training of the guns, and less 
likely to foul the screw" if shot away. 
Superheated Steam . — The researches of Dr. Fairbairn and Mr. Tate on 
