ed. The
original tubes may have been copper or brass since these were easier to
keep tight than the less malleable iron tubes. The present tube sheet is
of iron but was originally copper. Its thickness cannot be conveniently
measured, but it is greater than that of the boiler shell, probably
about 1/2 to 5/8 inch. While copper tubes and tube sheets were not much
used in this country after about 1870, copper was employed as recently
as 1950 by Robert Stephenson & Hawthorns, Ltd., on some small industrial
locomotives.

The boiler shell is lagged with wooden tongue-and-groove strips about
2-1/2 inches wide (felt also was used for insulation during this
period). The wooden lagging is covered with Russia sheet iron which is
held in place and the joints covered by polished brass bands. Russia
sheet iron is a planish iron having a lustrous, metallic gray finish.

[Illustration: Figure 14.--THE "FURY," BUILT FOR THE Boston and
Worcester Railroad in 1849 by Wilmarth. It was known as a "Shanghai"
because of its great height. (Smithsonian Chaney photo 6443.)]

[Illustration: Figure 15.--THE "NEPTUNE," BUILT FOR THE Boston and
Worcester in 1847 by Hinkley and Drury. Note the similarity of this
engine and the _Fury_.]

[Illustration: Figure 16.--THE "PIONEER" AS FIRST EXHIBITED in the Arts
and Industries building of the Smithsonian Institution prior to
restoration of the sandbox. (Smithsonian photo 48069D.)]

The steam dome (fig. 18) is located directly over the firebox, inside
the cab. It is lagged and jacketed in an identical manner to the boiler.
The shell of the dome is of 5/16-inch wrought iron, the top cap is a
cast-iron plate which also serves as a manhole cover offering access to
the boiler's interior for inspection and repair.

[Illustration: Figure 17.--"PIONEER" locomotive. (Drawing by J. H.
White.)]

[Illustration: Figure 18.--"PIONEER" LOCOMOTIVE, (1) Safety valve, (2)
spring balance, (3) steam jet, (4) dry pipe, (5) throttle lever, (6)
throttle, (7) crown bar, (8) front tube sheet, (9) check valve, (10) top
rail, (11) rear-boiler bracket, (12) pedestal, (13) rocker bearing, (14)
damper, (15) grate, (16) bottom rail, (17) pump heater valve, (18)
cylinder lubricator, (19) reversing lever, (20) brake shoe, (21) mud
ring, (22) blowoff cock, (23) ashpan. (Drawing by J. H. White.)]

A round plate, 20 inches in diameter, riveted on the forward end of the
boiler, just behind the bell stand, was found when the old jack