FLO 
FLO 
Weigleb found the common flint to con- 
tain 80 parts in the 100 silex, 18 alumina, 
and 2 lime. It is used in making glass and 
pottery. 
A solution of siliceous earth, made by 
fusing flints with a large proportion of fixed 
alkali, and dissolving the mass in water, is 
called liquor of flints. 
FLOAT of a fishing-line, the cork or 
quill that floats or swims above water. See 
Angling. 
Float also signifies a certain quantity of 
timber bound together with rafters, athwart, 
and put into a rivcf to be conveyed down the 
stream ; and even, sometimes, to carry 
burdens down a river with the stream. 
Float boards, those boards fixed to 
water-wheels of under-shot mills, serving to 
receive the impulse of the stream, whereby 
the wheel is carried round, See Mill. 
FLO ATTN G bodies are' those which swim 
on the surface of a fluid, the most interest- 
ing of which are ships and vessels employed 
in war and commerce. It is known to 
every seaman, of what vast moment it is to 
ascertain the stability of such vessels, and 
the positions they assume when they float 
freely on the surface of the water. To be 
able to accomplish this, it is necessary to 
understand the principles on which that sta- 
bility and these positions depend. A float- 
ing body is pressed downwards by its own 
weight in a vertical line passing through its 
centre of gravity ; and it is supported by 
the upward pressure of a fluid, which acts in 
a vertical line that passes through the centre 
of gravity of the part which is under the 
water ; and without a coincidence between 
these two lines, in such a manner as that 
both centres of gravity may be in the same 
vertical line, the solid will turn on an axis, 
till it gains a position in which the equili- 
brium of floating will be permanent. From 
this it is obviously necessary to find what 
proportion the part immersed bears to the 
whole, to do which the specific gravity of 
the floating body must be known, after 
which it must be found by geometrical me- 
thod, in what positions the solid can be 
placed on the surface of the fluid, so that 
both centres of gravity may be in the same 
vertical line, when any given part of the 
solid is immersed under file sift-face. These 
things being determined, something is still 
wanting, for positions may be assumed in 
which the circumstances now mentioned 
concur ; and yet the solid will assume some 
other position wherein it wall permanently 
float. However operose and difficult (says 
an able mechanic) the calculations neces- 
sary to determine the stability of nautical 
vessels may, in some cases be, yet they all 
depend upon the four following simple and 
obvious theorems, accompanied with other 
well known stereometrical and statical 
principles. 
Theorem 1. Every floating body dis- 
places a quantity of the fluid in which it 
floats, equal to its own weight ; and conse- 
quently, the specific gravity of the fluid will 
be to that of the floating body, as the mag- 
nitude of the whole is to that of the part 
immersed. 
Theorem 2. Every floating body is im- 
pelled downward by its own essential 
power, acting in the direction of a vertical 
line passing through the centre of gravity of 
the whole ; and is impelled upward by the 
re-action of the fluid which supports it, 
acting in the direction of a vertical line 
passing through the centre of gravity of the 
part immersed ; therefore, unless these two 
lines are coincident, the floating body thus 
impelled must revolve round an axis, either 
in motion or at rest, until the equilibrium is 
' restored, 
Theorem 3. If by any power whatever a 
vessel be deflected from an upright posi- 
tion, the perpendicular distance between 
two vertical lines passing through the cen- 
tres of gravity of the whole, and of the part 
immersed respectively, will be as the stabi- 
lity of the vessel, and which will be posi- 
tive, nothing, or negative, according as 
the metacentre is above, coincident with, 
or below the centre of gravity of the ves- 
sel. 
Theorem 4. The common centre of gra- 
vity of any system of bodies being given 
in position, if any one of these bodies be 
moved from one part of the system to 
another, the corresponding motion of the 
common centre of gravity, estimated in 
any given direction, will be to that of the 
aforesaid body, estimated in the same direc- 
tion, as the weight of the body moved is to 
that of the whole system. From whence it is 
evident, that in order to ascertain the sta- 
bility of any vessel, the position of the 
centres of gravity of the whole, and of that 
part immersed, must be determined ; with 
which, and the dimensions of the vessel, the 
line of floatation, and angle of deflection, 
the stability or power either to right itself 
or overturn, may be found. 
FLOOD, among seamen, is when the tide 
begins to come up, or the water begins to 
rise, then they call it young flood; after 
