5 
very unusual amount. The depression accompanying the 
Royal Charter storm was only about one-half that accompany- 
ing the past storm.” 
Mr. Alfred Fryer, who observed the movements of an 
aneroid barometer under the microscope during the storm, 
stated that the minimum pressure occurred at lOh. 10m. p.m., 
and that for some minutes before and after this time the 
index of the instrument Avas in a state of rapid vibration. 
A Paper was read by Dr. J. P. Joule, entitled, “ Notice 
of a Compressing Air Pump.” 
The Author referred to the difficulties of realising in 
practice the theoretical advantages of the air, or the super- 
heated steam engine. The abrasion which takes place when 
metal rubs against metal, Avithout an intermediate lubricator, 
speedily destroys the cylinder. He believed that the necessity 
of using elastic packing would not exist if the length of the 
channel along which the elastic fluid must pass, in order to 
arrive at the opposite side of the cylinder, Avere sufficiently 
increased. This might be accomplished byincreasing the depth 
of the piston, or by placing on the rim of the piston concentric 
rings to enter, at the beginning and end of each stroke, corre- 
sponding concentric grooves in the covers of the cylinder. 
The principle of great depth of piston, as a substitute for 
packing, had been successfully carried out in the pump which 
Avas the subject of this communication. The cylinders, two 
in number, are tAventy inches long and two inches in diameter. 
The pistons are solid cylinders of iron, ten inches long, fitting 
as accurately to the cylinders as is consistent Avith freedom 
of motion. The depth of each piston, as compared Avith 
its diameter, renders the usual guide or parallel motion 
unnecessary, so that the connecting rod is simply jointed 
to the top of the piston. Air is readily compressed to 
sixteen atmospheres, the quantity passing the sides of the 
cylinders being very trifling. 
