DEO 
equator have, of course, the same declina- 
tion. The declination then marks the situ- 
ation of a star north or south from the 
equator. Precision requires still another 
circle from which their distance, east or 
west, may be marked, in order to give the 
real place. The circle of declination, which 
passes through that point of the equator 
called the vernal equinoctial point, lias been 
chosen for that purpose. The distance of 
the circle of declination of a given star 
from that point measured on the equator, 
or the arc of the equator included between 
the vernal equinox and the circle of declin- 
ation of the star, is called its right ascension. 
If we know the declination and the right 
ascension of a star, we know its precise 
situation in the heavens. 
The declination of any star may be easily 
found by observing the following rule : Take 
the meridian altitude of the star, at any place 
where the latitude is known; the comple- 
ment of this is the zenith distance, and is 
called north or south as the star is north or 
south at the time of observation. Then, 
1. When the latitude of the place and 
zenith distance of the star are of different 
kinds, namely one north and the other 
south, their difference will be the declina- 
tion, and it is of the same kind with the 
latitude, when that is tlie greatest of the 
two, otherwise it is of the contrary kind. — 
2. If the latitude and the zenith distance 
are of the same kind, i. e. both north or 
both south, their sum is the declination ; 
and it is of the same kind with the latitude. 
See Globes, use of. 
Declination of a wall or plane for dials, 
is an arch of the horizon, contained either 
between the plane and the prime verticle 
circle, if you reckon it from the east or 
west ; or else between the meridian and the 
plane, if you account it from north or south. 
There are many ways given by authors for 
finding the declination of a plane, of which 
all those that depend upon the magnetic 
needle deserve to be suspected on many 
accounts. The common method, by find- 
ing the sun’s 'horizontal distance from the 
poll of the plane, is subject to many errors 
and difficulties. The way therefore we 
would recommend as the best for finding the 
declination of a plane, is by a dec! nator. 
DECLINATOR, or Declinatory, an 
instrument contrived for taking the de- 
cimations, inclinations, and reclinations of 
planes. See Instruments, mathemati- 
cal. 
DECLINING dials, those which do not 
DEC 
face directly any of the four cardinal points. 
See Dialing. 
DECOCTION, the boiling of one or 
more ingredients in' a watery fluid. See 
Pharmacy, 
DECOMPOSITION, in chemistry. The 
substance resulting from a chemical combi- 
nation is denominated a compound. The 
substances of which it is formed are called 
its constituent parts. When these are again 
separated, the process is denominated de- 
composition. See Analysis. 
DECOUPIjE , in heraldry, the same as 
uncoupled : thus, a chevron decouple, is a 
chevron wanting so much of it towards the 
point, that the tvyo ends stand at a distance 
from one another, being parted and un- 
coupled. 
^ DECOY, among fowders, a place made 
for catching ndld-fowl. A decoy is gene- 
rally made where there is a large pond .sur- 
rounded with wood, and beyond that a 
marshy and uncultivated country ; if the 
piece of water is not thus surrounded, it 
will be attended with noises and other acci- 
dents which may be expected to frighten the 
wild-fowl from a quiet haunt, where they 
mean to sleep in the day-time in security. 
If these noises or disturbances are wilful, it 
has been held that an action will lie against 
the disturber. As soon as the evening sets 
in, the decoy rises, and the wild-fowl feed 
during the night. If the evening is still, 
the noise of their wings during their flight 
is heard at a very great distance, and is a 
pleasing, though rather melancholy sound. 
The decoy ducks are fed with hemp-seed, 
which is thrown over the screens in small 
quantities, to bring them forwai'ds into the 
pipes or canals, and to allure the vrild-fowl 
to follow, as this seed is so light as to float. 
There are several pipes, as they are called, 
which lead up a narrow ditch that closes 
at last with a funnel-net. Over these pipes 
(which grow narrower from their first en- 
trance) is a continued arch of netting suspend- 
ed on hoops. It is necessary to have a pipe or 
ditch for almost eyqry wind that can blow, 
as upon this circumstance it depends which 
pipe the fowl will take to ; and the decoy- 
man always keeps on the leeward side of 
tlie ducks, to prevent his scent reaching 
their sapcious' nostrils. Ail along each 
pipe, at intervals, are placed screens made 
of reeds, which are so situated that it is im- 
possible the wild-fowl should see the decoy- . 
man before they have passed on towards w 
the end of the pipe, where the purse-net is 
placed. The inducement to the wild-fow! 
