e Beaumont engine, worked by compressed air, may be generally said to
be similar to that described in a paper read before the Society of Arts
on the 16th March, 1881, to which, however, some improvements have been
since introduced.

The apparatus for compressing the air was placed in the shed. The air was
compressed to 63 atmospheres by a pump worked by a steam engine, and
stored in cylindrical reservoirs of wrought iron without rivets. A pipe
led the air from the reservoirs to the head of the tramway, where the
cylinder placed on the motor for storing the air during the journey could
be conveniently charged.

The air was compressed by means of four pumps, placed two and two in a
water-box, and worked by the direct action of a compound engine, with
cylinders, placed in juxtaposition, of 8 in. and 14 in. diameter
respectively, with an equal length of stroke of 13 in.

TABLE I.

Krauss. Wilkinson. Rowan.
Diameter of cylinder.........d 5.5 in. 6.5 in. 5.1 in.
Length of stroke.............l 11.8 in. 9 in. 9.8 in.
Diameter of wheels...........D 31.5 in. 27.5 in. 29.5 in.
Pressure at which
boiler is worked...........P 220 lb. 147 lb. 191 lb.
(p(d^{2})l)/(2D).............E 1,210 lb. 1,509 lb. 805 lb.
Total heating surface........S 105 sq. ft. 105 sq. ft. 64 sq. ft.
Grate surface................G 2.7 sq. ft. 5.4 sq. ft. 3.1 sq. ft.
Surface of condenser.........C 274.482 s. ft. None. 861.120 s. ft.
Weight in running order
(motor only)...............P' 15,400 lb. 15,400 lb. 9,020 lb.
Weight in running order
(total)....................P" - - 15,400 lb.
Contents of water tank.......- 28.24 cub. ft. 13 cub. ft. 4.2 cub. ft.
Contents of coal bunks.......- 14.12 cub. ft. 12.5 cub. ft. 8.5 cub. ft.
P'/E 12.7 lb. 10.2 lb. 11.2 lb.
P"/E - - 19.125 lb.
P'/S 146 147 140
P'/G 5,722 2,855 2,889
C/S 2.6 - 13.4
C/G 102 - 275

The air, after being forced through the first pump cylinder, passed
successively through the other three, the diamet