504 ON THE EXPLOSION OF THE BOILER 
from the place where it stood, at the time of the 
explosion. Hence, therefore, it appears, that, 
after breaking the last tie-beam, the force of the 
Engine was exhausted; and that the Engine fell 
perpendicularly to the ground. It cannot be 
known to what height the engine was thrown: 
because, the force which broke the tie-beams 
would bring down the roof of the shed. 
6. The action of the steam, by which the Engine 
was moved, would be similar to that of the water 
in Barker’s mill; and, therefore, the motive force 
of the steam, in a direction perpendicular to the 
top of the fire-box, will be expressed by the area 
of the aperture, in the roof of the fire-box, mul- 
tiplied by the pressure of the steam on that area. 
The motive force of the steam will be diminished, 
as the density of the steam decreases; and the 
force of the steam will continue to act upon the 
Engine, until the pressure of the steam in the 
boiler becomes equal to the pressure of the at- 
mosphere. As the motive force of the steam is 
not applied to the Engine, at its centre of gravity, 
the Engine will revolve about its centre of gravity, 
in the same manner as if the motive force of the 
steam was applied to make the Engine revolve 
about a fixed axis, passing through its centre of 
es 
