arrangement of the gusset stays for the back plate of firebox casing and
for the smokebox tube plate will be seen. A grid is placed across the
smokebox just above the tubes, and provision is made, as shown in Figs.
1 and 4, for closing the top of the exhaust nozzle, and opening a
communication between the exhaust pipes and the external air when the
engine is run reversed. The chimney is 153/4 in. in diameter at its lower
end and 18.9 in. at the top. The chief proportions of the boiler are as
follows:

Sq. ft

Heating surface: Tubes 1598.5
Firebox 102.5
------
1701.0

Firegrate area 23.3 [1]
Sectional area through tubes (disregarding ferrules) 3.5
Least sectional area of chimney. 1.35
Ratio of firegrate area to heating surface. 1:73
Ratio of flue area through tubes to firegrate area. 1:6.7
Ratio of least sectional area of chimney to firegrate area. 1:17.26

[Transcribers note 1: Best guess, 2nd digit illegible]

The proportion of chimney area to grate is much smaller than in ordinary
locomotives, this proportion having no doubt been fixed upon to enable a
strong draught to be obtained with the engine running at a slow speed.
Of the general fittings of the engine we need give no description, as
their arrangement will be readily understood from our engravings, and