PRI 



PRO 



I 



near figure, as directed under these arti- 

 cles, and the sum of all these, taken to- 

 gether, is the whole superficies of the 

 prism. The solid content of a given 

 prism may be found thus : let the area of 

 the base of the prism be measured, as 

 directed under the ariicle ME-VSUKATIOX ; 

 and let this area he multiplied by the 

 height of the prism, and the product will 

 give the solid content of the prism. 



PRISM, in diuptrics, a triangular glass- 

 prism, much vised in experiments about 

 the nature of light and colours. See OP- 

 TICS. 



PIUSTIS, the seno-fsh, in natural his- 

 ton, a genus of fishes of the order Car- 

 tilaginei. It may be with more propriety 

 considered as a species of the squalus, or 

 shark, and as sue!) is regarded by Shaw. 

 The saw-fish inhabits the Mediterranean, 

 and was known to the Greeks and Ro- 

 mans by the name of pristis. It grows to 

 the length of sixteen feet, and the gene- 

 ral length of the snout is about one third 

 of that of the whole fish. There are 

 three varieties, in which the difference 

 is confined to the size and the snout. 



PRIVATEERS, in maritime affairs, a 

 kind of private ships of war, fitted out by 

 private persons at their own expense"; 

 who have leave granted them to keep 

 what they can take from the enemy, al- 

 lowing the Admiral his share. 



PRIVY council, is the principal coun- 

 cil belonging to the King, and is general- 

 ly called, by way of eminence, the coun- 

 cil. Privy Counsellors are made by the 

 King's nomination, without either patent 

 or grant ; and, on taking the necessary 

 oaths, they become immediately Privy 

 Counsellors, during the life of the King- 

 that chooses them, but subject to remo- 

 val at his discretion. No inconvenience 

 now arises from the extension of the 

 number of the Privy Council, as those 

 only attend who are especially summon- 

 ed for that particular occasion. 



PRIZE, in maritime affairs, a vessel 

 taken at sea from the enemies of a stale, 

 or from pirates ; and that either by a 

 man-of-war, a privateer, &c. having a com- 

 mission for that purpose. Vessels are 

 looked on as prize, if they fight under any 

 other standard than that of the state from 

 which they have their commission ; if 

 they have no charter-party, invoice, or 

 bill of lading a-board; if loaded with ef- 

 fects belonging to the King's enemies, or 

 with contraband goods. Those of the 

 King's subjects recovered from the ene- 

 my, after remaining twenty-four hours in 

 their hands, are deemed" lawful prize. 



Vessels that refuse to strike may be con- 

 strained ; and if they make resistance arid 

 fight, become lawful prize, if taken If 

 ships of war, the prizes are to be divided 

 among the officers, seamen, &c. as his 

 Majesty shall appoint by proclamation ; 

 but among privateers, the division is ac- 

 cording to the agreement between the 

 owners. By statute 13 George II, c. 4. 

 judges and officers, failing of their duty, 

 in respect to the condemnation of prizes, 

 forfeit 500/. with full costs of suits; one 

 moiety to the King, and the other to the 

 informer. 



PROBABILITY is nothing but the ap- 

 pearance of tiie agreement or disagree- 

 ment of two ideas, by the intervention of 

 proofs whose connection is not constant 

 and immutable, or is not perceived to be 

 so; but is, or appears for the most part 

 to be so ; and is enough to induce the 

 mind to judge the proposition true or 

 false, rather than the contrary. 



Of probability there are degrees, from 

 the neighbourhood of certainly and de- 

 monstration, quite down to improbability 

 and unlikeness, even to the confines of 

 impossibility; and also degrees of assent, 

 from certain knowledge, and, what is 

 next to it, full assurance and confidence, 

 quite down to conjecture, doubt, distrust, 

 and disbelief. That proposition then is 

 probable, for which there are arguments, 

 or proof, to make it pass or be received 

 for true. Probability being' then to sup- 

 ply the defect of oar knowledge, is al- 

 v\\-ys conversant about a thing whereof 

 we have no certainty, but only some in- 

 ducements to receive it for true. The 

 grounds of it are, in short, these two fol- 

 lowing : First, the conformity of any 

 thing with our own knowledge, experi- 

 ence, or observation. Secondly, the testi- 

 mony of others vouching their observa- 

 tion and experience. In the testimony 

 of others, is to be considered, 1. the 

 number; 2 the integrity ; 3. the skill of 

 the witnesses; 4. the design of the au- 

 thor, if it be a testimony cited out of a 

 book ; 5. the consistency of the parts and 

 circumstances of the relation; 6. contra- 

 ry testimonies. The mind, before it ra- 

 tionally assents or dissents to any proba- 

 ble proposition, ought to examine all the 

 grounds of probability, and see how they 

 make, more or less, for or against it; and", 

 upon a due balancing 1 the whole, reject 

 or receive it, with a more or less firm as- 

 sent, according to the preponderance of 

 the greater grounds of probability on one 

 side or the other. 



PROBABILITY of an event, in the Doc- 



