1824 ] 
true set and position of a lug-sail, with- 
out dipping the yard in stays, for there 
is not any inherent difference between 
those two sails, besides that which re- 
sults from the different methods in 
which they are slung, as the peak or 
slope at the head of the lug-sail is not 
essential to its proper effect. The cause 
and nature of the defects of the square- 
sail, and the principle, from which the 
lug-sail derives its superior powers, shall 
now be explained. \ 
The experiment upon the square-sail, 
made and published by Captain Gower, 
of the Honourable East-India Com- 
pany’s Service, demonstrates that the 
main pressure of the wind against a 
square-sail, close hauled, is in its wea- 
ther half, consequently the parl and hal- 
yard should then attach to that part of 
the weather yard-arm at which the wind 
chiefly operates, and ought not to be 
always fixed to the middle of the yard; 
by this improper mode of slinging the 
yard of a square-sail, it is subjected to 
its present defects, as the main pressure 
of the wind against a square-sail, as 
now slung, is to windward of the mast 
and causes the sag or belly of the 
sail to begin in the /uff, which therefore 
lifts with the wind sooner than the luff 
of any other sail, and requires to be 
kept further from the wind, and assisted 
with bowlines to keep it full. The 
same cause makes the after leach of a 
Square-sail operate as a back-sail to 
retard the ship, increase her lee-way, 
and prevents the escape of the dead wind 
that has spent its force upon the wea- 
ther-half of the sail. The equality of 
strain that is cast upon the tack and 
the sheet of a square-sail, also cause it 
to retain the dead or spent wind, and 
whatever send or sway of the yard is 
left by the braces, being in the weather 
yard-arm, is unfavourable to the pro- 
gress of the ship to windward.. These 
concurring effects of slinging a square- 
sail by the middle of the yard, destroy 
about one-fifth of its windwardly power 
when close-hauled; and presently it 
shall be shown, that from the same 
cause the square-sail loses one-sixth of 
its propelling power when before the 
wind. The difference of opinion that 
exists among seamen upon the ques- 
tion, whether the weather or the lee-lift 
of a square-sail should be kept tought, 
proves that the cause of its defects is 
not generally understood, and that the 
application of a scientific principle is 
hecessary to give consistency to practice. 
On the other hand, the lug-sail being 
Miller on the Sailing Properties of Square-Rigged Ships. 
2l1 
slung at its supposed fulcrum, in the 
proportion of one third of the yard to 
windward of the mast, where the main 
pressure of the wind operates, and of 
two thirds to leeward of the mast, the 
weight of that greater proportion of the 
yard and sail to leeward, casts a per- 
pendicular strain upon the luff of the 
sail, which therefore meets the wind at 
a more acute angle than the luff of the 
square-sail, and does not lift so soon as 
the latter with the wind; that greater 
weight to leeward of the mast also pre- 
vents any superfluous strain upon the 
after-leach of the lug-sail, which there- 
fore gives a vent to the dead or 
spent wind, and does not operate as a@ 
back-sail, and the sway of the lee yard- 
arm, in consequence of its greater length, 
sends the vessel to windward and a-head, 
the main resistance of the water being 
against the lee-bow of a vessel close- 
hauled. 
These great advantages are derived 
by the lug-sail from the scientific 
principle on which it is slung, the 
yard intersecting the mast at the point 
velique, as the French term it: that is, 
the point at which the line of resistance 
of the water at the bows of the vessel, 
intersects the line of the main pressure 
of the wind upon her sails, which point 
would be evidently at the intersection 
of the yard and mast of a vessel carry- 
ing but one lug-sail, when she sails close 
to the wind with her helm amidship, 
as she would do if the mast be step-~ 
ped in the proper place: and that would 
be found in the fore-hold, more or less 
advanced according to the mould of the 
vessel, 
So true is the superiority of this prin- 
ciple of the lug-sail, though so little un- 
derstood, or adopted, that even the Chi- 
nese have some idea of it, as the square- 
sails of their junks are slung somewhat 
like a lug-sail, at a point some little dis- 
tance from the middle of the yard, in 
the proportion apparently of about two- 
fifths to windward, and three-fifths to 
leeward of the mast; and the frames 
that spread the sails of a common wind- 
mill are fixed to the arms of the mill in 
nearly the same proportions; but it ap- 
pears that the Chinese sometimes carry 
the longer yard-arm to windward when 
close-hauled, from not knowing that the 
point at which the yard is suspended, 
should coincide with the line of the 
main pressure of the wind; which occa- 
sional misapplication of the principle 
probably arises from a notion that the 
method described gives greater stiffness 
2E 2 or 
