PLO 



PLU 



sion of the first scale is subdivided into 

 fen equal parts, to which is prefixed the 

 number 10, signifying 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, denot- 

 ing that sixteen of these subdivisions make 

 an inch. The first division of the third 

 scale is subdivided in like manner irrto 

 10, to which is prefixed the number 20; 

 to that of the fourth scale is prefixed the 

 number 24 ; to that ot the fifth, 32 ; that 

 of tlie sixth, 40; that of the seventh, 48; 

 denoting the number of subdivisions equal 

 to an inch, in each, respectively. The 

 two last scales are broken off to make 

 room for two lines of chords- There is, 

 also, on the back side of the instrument a 

 diagonal scale. 



As to the use of 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 an inch, extend 

 the other to five of the subdivisions, for 

 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 

 off from a greater or lesser scale, i. e,. 

 from a scale that has more or fewer divi- 

 sions in an inch. 



To find the chains and links contained 

 in a right line, e. gr. that is just drawn, 

 according to any scale, e. gr. that of 20 

 in an inch. Take the length of the line 

 in the compasses, 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. 

 Generic 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 mal- 

 lard, 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 ser- 

 pents. 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 be seen on the most 

 elevated trees, where it shs 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 cor- 

 responding 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 atU mpt 

 at destroying a fly by the ds-.rt of its bill 

 it lias been observed to succeed tor a long 

 continued time. It is often domesticated, 

 and is called the sun -bird, from the cir- 

 cumstance, probably, of its or.n deve- 

 loping at once its tail and wint's, and 

 thus exhibiting a circular appearance of 

 plumage, which, however, is certainly by 

 no means Blowing and aident. 



PLOUGH, in agriculture, a machine 

 for turning up the soil, contmed to save 

 the time, labour, and expence, that With- 

 out this instrument must have been em- 

 ployed in digging land, to prepare it tor 

 the sowing of all kinds of grain. See 

 AGRICULTURE, 



PLOUGH, among book-binders, is a 

 machine for cutting 1 the edges of the 

 leaves of books smooth. 



PLUKENETIA, in botany, so named 

 from Leonard Piukenet, a genus of the 

 Monoecia Monadelphia class and order. 

 Natural order of Tricoccae Euphorbias, 

 Jussieu. Essential character ; calyx 

 none ; petals four ; male, stamens eight : 

 nectaries four, bearded : female, style 

 very long, with a peltate, four-lobed stig- 

 ma ; capsule four-grained. There is but 

 one species ; viz. V. volubilis, a native of 

 both Indies. 



PLUM-tree. See PRUNUS 



FLUMB'line, among artificers, denotes 

 a perpendicular to the horizon ; so called 

 as being commonly erected by means of 

 a plummet. 



PLUMBAGO, in botany, lead-wort, a 

 genus of the Pentandria Monogynia class 

 and order. Natural order of Plumba- 

 gines, Jussieu. Essential character : co- 

 rolla funnel-form ; stamens inserted into 

 scales inclosing the base of the corolla ; 

 stigma five-cleft ; seed one, oblong, tuni 

 cated. There are seven species. 



PLUMBAGO, in chemistry, a carburet 

 of iron. See IRON. 



PLUMBERY, the art of casting 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, 



