PLO 
into equal parts. The first division of the 
first scale is subdivided into ten equal parts, 
to which is prefixed the number 10, signify- 
ing that ten of these subdivisions make an 
inch ; or that the divisions of that scale are 
decimals of inches. The first division of 
the second scale is likewise subdivided into 
10, to which is prefixed the number 16,' de- 
noting that sixteen of these subdivisions 
make an inch. The first division of the 
third scale is subdivided in like manner into 
10, to which is prefixed the number 20 ; to 
that of the fourth scale is prefixed the num- 
ber 24 ; to that of the fifth, 32 ; that of the 
sixth, 40 i that of the seventh, 48 ; denoting 
the number of subdivisions equal to an inch, 
in each, respectively. The two last scales 
are broken otF to make room for two lines 
of chords. There is also oh the back side 
of the instrument a diagonal scale. 
As to the use of the plotting, if we were 
required to lay down any distance upon 
paper, suppose 6 chains 50 links : draw an 
indefinite line ; then setting one foot of the 
compasses at figure 6 on the scale, e. gr. 
the scale of 20 in ah inch, extend the other 
to 5 of the subdivisions, for the 50 links : 
this distance, being transferred to the line, 
will exhibit the 6 chains 50 links required. 
If it be desired to have 6 chains 50 links 
take up more or less space, take them olF 
from a greater or lesser scale, i. e. from a 
scale that has more or fewer divisions in an 
inch. 
To find the chains and links contained in 
a right line, e. gr. that is just drawn, accord- 
ing to any scale, e. gr. that of 20 in an inch. 
Take the length of the line in the com- 
passes, and applying it to the given scale, 
you will find it extend from the number 6 
of the great divisions to 5 of the small ones : 
hence the given line contains 6 chains 50 
links. 
PLOTUS, the darter, in natural history, 
a genus of birds of the order Anseres. Ge- 
neric character : bill strait, pointed toothed ; 
nostrils, a slit near the base ; face and chin 
without feathers ; legs short ; toes four, and 
all webbed. There are three species. P. 
anhinga, or the white bellied darter, is of 
the size of a mallard, but measures nearly 
three feet in length. It is found in Brazil; 
builds in trees, and roosts in them at night, 
though living chiefly on fishes. In catching 
these its manner resembles that of serpents. 
Drawing up its neck, it darts on its prey 
with its bill, and catches it in its claws. It 
is rarely seen on the ground, and, when not 
on the water in the pursuit of its food, it is to 
PLU 
be seen on the most elevated trees, where it 
sits with its head drawn in between the 
shoulders. Its flesh is rank and oily. The 
black-bellied anhinga is found in Ceylon 
and Java, and darting its long neck through 
the low shrubs immediately over the water, 
is, on the first view, mistaken frequently 
for some venomous reptile, and excites 
corresponding agitation and terror. The 
Surinam darter is of the size of a teal, and 
feeds on flies as well as fishes and water 
insects ; and in every attempt at destroying 
a fly by the dart of its bill it has been ob- 
served to succeed for a long continued time. 
It is often domesticated, and is called the 
sun-bird, from the circumstance, probably, 
of its often developing at once its tail and 
wings, and thus exhibiting a circular ap- 
pearance of plumage, which, however, is 
certainly by no means glowing and ardent. 
PLOUGH, in agriculture, a machine for 
turning up the soil, contrived to save the 
time, labour, and expence that without this 
instrument must have been employed in 
digging land, to prepare it for the sowing of 
all kinds of grain. See Agriculture. 
Plough, among bookbinders, is a ma- 
chine for cutting the edges of the leaves of 
books smooth. 
PLUKENETIA, in botany, so named 
from Leonard Plukenet, a genus of the 
Monoecia Monadelphia class and order. 
Natural order of Tricoccas. Euphorbiae, 
Jussieu. Essential character : calyx none ; 
petals four; male, stamens eight; nectaries 
four, bearded : female, style very long, with 
a peltate, four-lobed stigma ; capsule four- 
grained. There is but one species; viz. P. 
volubilis, a native of both Indies. 
PLUM-tree. See Prunus. 
PLUMB-Kne, among artificers, denotes a 
perpendicular to the horizon ; so called as 
being commonly erected by means of a 
plummet. 
PLUMBAGO, in botany, had-wort, a 
genus of the Pentandria Monogynia class 
and order. Natural order of Plumbagines, 
Jussieu. Essential character : corolla funnel- 
form ; stamens inserted into scales inclosing 
the base of the corolla; stigma five-cleft; 
seed one, oblong, tunicated. There are 
seven species. 
Plumbago, in chemistry, a carburet of 
iron. See Iron. 
PLUMBERY, the art of citing and 
working lead, and using it in buildings, &c. 
As this metal melts very readily, it is easy to 
cast it into figures of any kind, by running 
it into moulds of brass, clay, plaster, &6. 
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