AERONAUTICAL WORK. 41 
ing chamber, which is determined by the pressure in the holder 
causing the induced current of air for combustion. This cycle of 
events is readily disarranged. The cure that suggests itself is to 
make the holder of large capacity, and charge it with about one 
of spirit and four of compressed air by volume, placing a cock 
between the holder and the discharging orifice. The vaporising 
must be effected between the orifice and the cock, preferably by 
means of a few turns of the pipe at the point where the mixed 
air and spirit vapour begins to burn. That is, on the principle 
of the Wells, Doty, Denny, or Moeller and Condrup lights and 
burners, 
The twin-screws and gear weigh 3°75 ounces, which is the same 
as the single screw, shaft, and crank shaft coupling. The best 
results have been produced by the single screw. The screws have 
flat blades and the pitch is varied by twisting them in the tin 
sleeve that represents the boss. The long blade and fine pitch is 
thought to be most effective ; but this may not be true, as the 
back pressure on the pistons prevents a high piston speed being 
attained. 
A weight driven thrust measuring and recording apparatus for 
comparing the screws was tried and showed, amongst other things, 
that the effective pressure on the pistons, necessary to produce ‘64 
pounds of thrust and 340 revolutions per minute, was only 10-9 
pounds per square inch. 
The lubricator is unscrewed, partly filled with oil, and replaced 
before each trial. Live steam condenses in the lubricator, and 
the oil overflows into the valve cover and thence through the 
engine, 
The valve in the first instance was made of brass ; it used to 
©ut up the cylinder face and valve cover. The steel valve now in 
Position works satisfactorily. A spring was on the back of the 
valve cover and made it in effect a safety valve. The spring has 
been removed, and the bridge now holds the valve cover by two 
hooks to the steam pipe of the top cylinder and the post that 
“upports the engine on the top of the water tank. 
