54 Mr. Atwood's Propositions determining the Positiotis 
not to be considered in this place), the figure of the floating 
body, and the particular object of inquiry, must determine to 
which of these axes the motion of the solid is to be referred, 
when it changes its position : thus, suppose a square beam of 
timber, the specific gravity of which is to that of water as 1 
to 2, should be placed on the surface of that fluid with one of 
the flat surfaces parallel to the horizon (the length being as- 
sumed considerably greater than the breadth), no motion of 
rotation can take place round the transverse axis, by which 
the extremities of the beam would be elevated or depressed : 
but the solid will spontaneously revolve in this instance round 
the longer axis, changing its position until it settles with an 
angle upward. 
In like manner, if the same solid should be placed horizon- 
tally on the surface of the water with an angle upward, it will 
not spontaneously change its position ; but if one extremity of 
the beam should be forcibly elevated, and the other depressed, 
so as to incline the longer axis to the horizon, as soon as all 
external force is removed, the beam will revolve on a transverse 
horizontal axis, passing through the centre of gravity, and per- 
pendicular to the longer axis, until it settles in such a position 
as to leave the longer axis horizontal. These are instances in 
which the figure of the body, and the particular nature of the 
case, determine the axis round which the solid revolves, while 
it changes its situation on a fluid’s surface; this axis is called, 
for the sake of distinction, the axis of motion. 
The axis of motion, round which the solid revolves, having 
been determined, and the specific gravity being known, it ap- 
pears from the preceding observations, that the positions of 
permanent floating will be obtained, first by finding the 
