SLli 
IS bolted to the rnng-heads, and the iipjia' 
most to the futtocks and rungs. 
SLINO, an instrument serving for cast- 
ing stones with great violence. The in- 
habitants of tlie Balearic islands were famous 
in antiquity, for the dexterous management 
Of the sling; it is said they bore three 
kinds of slings, some longer, others slidrterj 
which they used according as their enemies 
were either nearer or more remote. It is 
added, that the first served them for a head 
band, the second for a girdle, and that a third 
they constantly carried with tliemm tliehand. 
Slings of a yard, ropes fixed round its 
middle, and serving to suspend it for the 
greater ease of working, or for security in 
an engagement ; in the latter case they 
usually add iron chains to the slings of the 
lower yards. Boat-slings, are strong ropes 
furnished with hooks and iron thimbles, by 
which to hook tiie tackle, in order to hoist 
the boats in or out of the ship ; tlie hooks of 
the slings are applied to ring bolts fixed in 
the keel, and extremities of the boat. 
SLINGING is used variously at sea, hut 
chiefly for tlie hoisting up casks, or other 
heavy things, with slings, i. e. contrivances 
of ropes spliced into tliemselves, at either 
end, with one eye big enough to receive 
the cask, or other thing, to be slung. 
SLOANEA, in botany, so named in me- 
mory of Sir Hans Sloane, Bart,, a genus of 
the Polyandria Monogynia class and order. 
Natural order of Amentacea. Tiliaceae, 
Jussieu. Essential character: calyx, one- 
leafed,from five to nine- cleft ; corolla none ; 
anthers growing to tJie filaments, below the 
top ; capsule echinate, from tliree to six 
celled, from three to six valved ; seeds two 
in a berried aril. There are three species. 
SLOATH or Sloth. See Bradypus. 
SLOOP, in naval affairs, a small vessel, 
furnished with one mast, the main sail of 
which is attached to, a gaff above, to the 
mast on its foremost edge, and to a boom 
below, it differs from a cutter by having a 
fixed steering how-sprit, and a jib-stay: 
the sails also are less in proportion to the 
size of the vessel. Sloops of war are vessels 
commanded by officers in a middle rank 
between a lieutenant and a post captain: 
these are styled masters and commanders. 
They carry from ten to eighteen guns, and 
are variously rigged as ships, brigs, schoon- 
ers, and sometimes cutters. 
SLUICE, in hydraulics, a frame of tim- 
ber, stone, earth, &c. serving to retain and 
raise the water of the sea, a river, &c. 
SLtf 
and on occasion to let it pass: such is the 
sluice of a mill, which stops and collects 
the water of a rivulet, &c. in order to dis- 
charge it at length, in greater plenty, upon 
the mill-wheel : such also are those used in 
drains, to discharge water off lands ; and 
such are the sluices of Flanders, &c. which 
serve to prevent the waters of the sea over* 
flowing the lower lands, except when there 
is occasion to drown them. Sometimes 
there is a canal between two gates or 
sluices, in artificial navigation, to save the 
water, and render the passage of boats 
equally easy and safe, upwards and down- 
wards; as in the sluices of Briare, in 
France, which are a kind of massive walls, 
built parallel to each other at the distance 
of twenty or twenty-four feet, closed with 
strong gates at each end, between which is 
a kind of canal or chamber, considerably 
longer than broad, wherein, a vessel being 
inclosed, the water is let out at the first 
gate, by which the vessel is raised fifteen 
or sixteen feet, and passed out of this canal 
into another much higher. By such means 
a boat is conveyed out of tlie Loire into 
the Seine, thougti the ground between 
them rise above one hundred and fifty feet 
higher than either of those risers. 
Tlie construction of sluices ought to bo 
conducted by an able engineer, who is well 
acquainted with the action of fluids in gene- 
ral; and particularly wiflt the situation of 
the place, the nature of the soil, &c. whore 
the sluice is to be erected ; if on the sea- 
shore, he ought to be perfectly well ac- 
quainted with the effects of the sea on that 
coast, and the seasons when it is calm or 
stormy, that he may be able to prevent the 
fatal accidents thence arising : and, if in a 
river, it is necessary to know whether it 
usually overflows its banks, and at what 
seasons of the year itS waters are highest 
and lowest. The machines for driving the 
piles should be placed about forty yards 
from the side of tlie sluice, above and be- 
low it. As to the depth of sluices, it must 
be regulated by the uses for which they are 
designed ; thus’ if a sluice is to be erected 
at tlie entrance of a bason for shipping, its 
depth must correspond with the draught of 
water of the largest ship that may, at any 
time, have occasion to enter thereby. The 
rule usually observed, is to make the sur- 
face of the bottom of the canal on a level 
with the low water mark : but if the bot- 
tom of the harbour and canal be such, as 
to be capable of becoming deeper by the 
action of the water, Belidor very justly oh- 
