of steam chest 1.5 cubic feet.

276. _Q._--These proportions do not apply to locomotive boilers?

_A._--Not at all. In locomotive boilers the draught is maintained by the
projection of the waste steam which escapes from the cylinders up the
chimney, and the draught is much more powerful and the combustion much more
rapid than in cases in which the combustion is maintained by the natural
draught of a chimney, except indeed the chimney be of very unusual
temperature and height. The proportions proper for locomotive boilers will
be seen by the dimensions of a few locomotives of approved construction,
which have been found to give satisfactory results in practice, and which
are recorded in the following Table:

Name of Engine

Great Britain. Pallas. Snake. Sphinx.
Diameter of cylinder 18 in. 15 in. 14-1/4 in. 18 in.
Length of stroke 24 in. 20 in. 21 in. 24 in.
Diameter of driving wheel 8 ft. 6 ft. 6-1/2 ft. 5 ft.
Inside diameter of fire box 53 in. 55 in. 41-1/3 in. 44 in.
Inside width of fire box 63 in. 42 in. 43-1/4 in. 39-1/2in.
Height of fire box above bars 63 in. 52 in. 48-1/3 in. 55-1/2in.
Number of fire bars 29 ... 32 16
Thickness of fire bars 3/4 in. 1-3/4 in. 5/8 in. 1 in.
Number of Tubes 305 134 181 142
Outside diameter of tubes 2 in. 2 in. 1-7/8 in. 2-1/8
in.
Length of tubes 11 ft 3 in 10 ft 6 in 10 ft 3-1/2 in. 14
ft 3-1/4 in.
Space between tubes 1/2 in. 3/4 in. 1/2 in.
Inside diameter of ferules 1-9/16 in. 1-1/2 in. 1-5/16 in. 1-5/8 in.
Diameter of chimney 17 in. 15 in. 13 in. 15-1/2 in.
Diameter of blast orifice 5-1/2 in. 4-5/8 in. 4-1/2 in. 4-3/4 in.
Area of grate 21 sq. ft. 16.04 sqft 12.4 sq. ft. 10.56
sq. ft
Area of air space of grate 11.4 sqft 4.08 sqft 5.54 sq. ft. 5
sq. ft.
Area of tubes 5.46 sqft 2.40 sqft 2.8 sq. ft.