by Marestier
and in the Vail account books and what the graphic scale in
Marestier's engine drawings produce, the exact dimensions of the
engine are uncertain. Nevertheless, they can be approximated with
enough accuracy for our purpose. As a result of this treatment, it
seems fully apparent that the engine was abaft the paddle wheel shaft,
with frame extending abaft the mainmast on the lower deck; there does
not appear to be a practical alternative in the light of the available
evidence. This matter will be referred to again.

The size of the cylinder and its valve chest and the inclined position
of the cylinder indicate conclusively that the valve chest was in the
mainhatch, which would normally be just forward of the mainmast. Even
then, the after flange of the cylinder would just clear the lower
deck, allowing 6 feet between decks, as in the _Ohio_. The cylinder
would have been about 6 feet long; the graphic scale indicated 6 feet
3 inches. The diameter of the cylinder plus height of valve chest
seems to have been 5 feet 9 inches to 6 feet. Because of the use of
the crosshead and a connecting rod, pivoted at crosshead, the
oscillating rod (or pitman) and piston together equalled twice the
stroke plus allowance for stuffing box, crosshead, and pitman
bearings. Therefore, the engine's over-all length, from head of
cylinder to the centerline of the side paddle wheel shaft, could not
have been much less than 15 feet 9 inches, and probably as much as 16
feet 2 inches, thus making the length at extreme clearance of crank
throw as much as 19 feet. These dimensions indicate that the
centerline of the side paddle wheel shaft must have been from 38 to 39
feet from the forward perpendicular. It is not clear how the wheel
shaft was mounted in the vessel. Taking into consideration her depth
and her reported draught, light and loaded, the Marestier sketch, and
the hull structure then used, it seems reasonable to place the
centerline of the shaft (which seems to have been about 7 to 8 inches
square) about 12 inches above the upper (or spar) deck to allow proper
dip of the blades. This position would have given proper blade
immersion at the mean draught of 13 feet.

In order to get the engine below deck, and to get the boiler or
boilers placed, it was necessary to cut a large opening in the two
decks. It may be assumed that this opening was big enough to take the
cylinder, without valve chest, and also the boilers, which went into