TRU 



run 



other figure. The protractor is a small 

 semi-circle of brass, or other solid mat- 

 ter, the limb or circumference of which 

 is nicely divided into one hundred and 

 eighty degrees: it serves not only to 

 draw angles on paper, or any plane, but 

 also to examine the extent "of those al- 

 ready laid down. For this last purpose, 

 let the small point in the centre of the 

 protractor be placed above the angular 

 point, and let the side coincide with one 

 of the sides that contain the angle pro- 

 posed; then the number of degrees cut 

 off by the other side, computing on the 

 protractor, will show the quantity of the 

 angle that was to be measured. See 

 MENSURATION. 



Protractors are now more usually made 

 in the form of a parallelogram, and pro- 

 perly graduated at the upper edge. See 

 MATHEMATICAL Instruments. 



PROVIDENCE, the conduct and di- 

 rection of the several parts of the uni- 

 verse, by a superior intelligent being. 



PROVINCE, in law, means the circuit 

 of an Archbishop's jurisdiction, which is 

 subdivided into bishoprics. The eccle- 

 siastical division of this kingdom is into 

 two provinces ; viz. Canterbury and 

 York. Provincial constitutions, in this 

 kingdom, were decrees made in the pro- 

 vincial synods, held under divers Arch- 

 bishops of Canterbury. 



PROVISO, in law, is a condition in- 

 serted in a deed, upon the observance of 

 which the validity of the deed depends. 



PROVOST marshal, an officer of the 

 King's navy, who has charge of the King's 

 prisoners taken at sea. 



PROVOST, or PREVOT, in the King's 

 stables ; his office is to attend at court, 

 and hold the King's stirrup, when he 

 mounts his horse, &,c. There are four 

 provosts of this kind, each of whom at- 

 tends in his turn monthly. 



PROW, in navigation, denotes the 

 head or fore-part of a ship, particularly in 

 a galley, being that which is opposite to 

 the poop or stern. In the middle of the 

 prow is the beak that cuts the water, on 

 the top of which is commonly some 

 figure or hieroglyphic. The prow is 

 lower than the poop, and contains fewer 

 decks. 



PRUNELLA, in botany, self-heal, a 

 genus of the Didynamia Gymnospermia 

 class and order. Natural order of Ver- 

 ticillatae, or Labiatae. Essential character : 

 filaments forked, with an anther on one 

 of the forks; stigma bifid. ' There are 

 three species. 



sal, in pharmacy, a prepara- 



tion of purified saltpetre, called also 

 crystal mineral, made in this manner : 

 having melted any quantity of saltpetre, 

 cast a little flower of sulphur upon it, 

 and when that is burnt throw on more ; 

 and continue to do so till the nitre flow 

 as clear as rock-water. Then with a clean 

 iron or brass ladle take it out, and, put- 

 ting it into moulds till coagulated, pre- 

 serve it for use. 



PRUNING, in gardening and agricul- 

 ture, is the lopping off the superfluous 

 branches of trees, in order to make them 

 bear better fruit, grow higher, or appear 

 more regular. Pruning, though an opera- 

 tion of very general use, is nevertheless 

 rightly, understood by few ; nor can it be 

 learned by rote, or, indeed, wholly by 

 books, but requires a strict observation 

 of the different manners of growth of the 

 several sorts of fruit-trees; the proper 

 method of doing which cannot be known, 

 without carefully observing how each kind 

 is naturally disposed to produce its fruit ; 

 for some do this on the same year's wood, 

 as vines ; others, for the most part, upon 

 the former year's wood, as peaches, nec- 

 tarines, See. and others, upon spurs which 

 are produced upon wood of three, four, 

 &.c. to fifteen or twenty years old, as 

 pears, plumbs, cherries, &c. therefore, in 

 order to the right management of fruit- 

 trees, provision should always be made 

 to have a sufficient quantity of bearing 

 wood in every part of the trees, and at 

 the same time there should not be a su- 

 perfluity of useless branches, which 

 would exhaust the strength of the trees, 

 and cause them to decay in a few years. 

 The reasons for pruning of fruit-trees 

 are, 1. To preserve them longer in a 

 vigorous bearing-state ; 2. To render 

 them more beautiful ; and, 3. To cause 

 the fruit to be larger and better tasted. 



PRUNUS, in botany, bird chary-tree, a 

 genus of the Icosandria Monogynia class 

 and order. Natural order of Pomacex. 

 Rosaceae, Jussieu. Essential character: 

 calyx five-cleft, inferior; petals five; 

 drupe with a nut, having the sutures pro- 

 minent There are thirty -three species. 



PRUSSIAN blue. A rich pigment has 

 been known for a considerable time un- 

 the name of Prussian blue. It is pre- 

 pared by drying blood, and mixing three 

 parts of the dried residuum "with two 

 parts of the potash of commerce, and 

 calcining the mixture in a crucible by 

 a red heat : it is then boiled in successive 

 portions of water, which are afterwards 

 mixed together, and concentrated by 

 evaporation. A solution is prepared of one 



