MARITIME OBSERVATIONS. 205 
fuppofe the fail fet in an angle of 45 degrees with the 
keel, as in the following figure; wherein 
AB reprefents the body of the veffel, CD the finch 
pofition of the fail, EEE the direction of the 
wind, MM the line of motion. In obferving this figure 
it will appear, that fo much of the body of the veffel as is 
immerfed in the water, muft, to go forward, remove out of 
its way what water it meets with between the pricked lines 
FF. And the fail, to go forward, muft move out of its 
way ail the air its whole dimenfion meets with between 
the pricked lines CG and DG. Thus both the fluids give 
refiftance to the motion, each in proportion to the quantity 
of matter contained in the dimenfion to be removed. And 
though the air is vaftly lighter than the water, and there- 
fore more eafily removed, yet the dimenfion being much 
greater its effect is very confiderable. 
It is true that in the cafe ftated, the refiftance given by 
the air between thofe lines to the motion of the fail is not 
apparent to the eye, becaufe the greater force of the wind 
which ftrikes it in the dire@ion EEE, overpowers its 
effet, and keeps the fail full in the curve a, a,a, a, a. 
But fuppofe the wind to ceafe, and the veflel in a calm 
to be impelled with the fame fwiftnefs by oars, the fail 
would then appear filled in the contrary curve b, b, b, b, 
b, when prudent men would immediately perceive that 
the air refifted its motion, and would order it to be taken 
in. 
Is there any poffible means of diminifhing this refift- 
ance, while the fame quantity of fail is expofed to the ac- 
tion of the wind, and therefore the fame force obtained 
from it? I think there is, and that it may be done by di- 
viding the fail into a number of parts, and placing thofe 
parts in a line one behind the other ; thus inftead of one 
{ail extending from C to D, figure 2, if four fails 
containing together the fame quantity of canvas, were 
placed as in figure 3, each having one quarter of the di- 
Pipe 2 mentions 
