row 



POW 



man pound, without food ; and it would 

 seem well, if there could be some remedy 

 in this respect, and the constable or others 

 were bound to give them sufficient food, 

 to be repaid by the owner. 



The use of the pound is, to put cattle 

 in which have been taken trespassing on 

 other persons lands, and they are to re- 

 main there for some days, when the lord 

 of the manor takes the cattle in his pos- 

 session, and they are cried in three neigh- 

 bouring market towns, and if not claimed 

 within a year and a day, are sold as es- 

 trays, and the damage they have done is 

 paid out of the produce. 



POURSUIVANT,or PURSUIVANT, in 

 heraldry, the lowest order of officers at 

 arms. See COLLEGE and HERALDRY. 

 The poursuivants are properly attendants 

 on the heralds, when they marshal pub- 

 lic ceremonies. Of these, in England, 

 there were formerly many ; but at pre- 

 sent are only four, viz. Blue-mantle, Rouge 

 cross, Rouge-dragon, and Portcullice. 

 In Scotland, there is only one king at 

 arms, who is stiled Lion, and has no less 

 than six heralds, and as many pursui- 

 vants, and a great many messengers at 

 arms, under him. 



POWDER, a dry medicine, well bro- 

 ken, either in a mortar, by grinding, or 

 by chemical operations. See PHARMACY. 

 POWDER, fulminating. When three 

 parts of nitre, two parts of potash, and one 

 of sulphur, are previously well dried, and 

 mixed together by trituration, they form 

 a compound which is known by the name 

 of fulminating powder. A few grains of 

 this mixture exposed to heat in an iron 

 ladle, first melt, assuming a darker co- 

 lour ; and when the whole is in fusion, 

 there is a violent explosion. The heat 

 should be applied slowly and gradually, 

 till it is completely fluid, and then, by 

 bringing it nearer the heat, the full effect 

 of the explosion is obtained. This com- 

 bustion and explosion are also owing to 

 the instantaneous evolution of elastic 

 fluids. The potash unites with the sul- 

 phur, and forms a sulphuret, which, with 

 the assistance of the nitre, is converted 

 into sulphurated hydrogen. At a certain 

 temperature, the sulphurated hydrogen 

 gas is disengaged, along with the oxygen 

 gas of the nitre, and suddenly taking fire, 

 strikes the air by the explosion which ac- 

 companies the evolution of the gases. 

 When the mixture is made with equal 

 parts of nitre and solid sulphuret of pot- 

 ash, the detonation is more rapid, but the 

 explosion is less violent. With three parts 

 of nitre, one of sulphur, and one of saw- 

 VOL. V, 



dust, well mixed together, what is called 

 powder of fusion is formed. If a little 

 of this powder is put into a walnut-shell, 

 with a thin plate of copper rolled up, and 

 the mixture set fire to, it detonates rapid- 

 ly, and reduces the metal to a sulphuret, 

 without any injury to the shell. 



POWER, in mechanics, denotes any 

 force, whether of a man, a horse, a 

 spring, the wind, water, 8tc. which being 

 applied to a machine, tends to produce 

 motion. 



The intensity of a power is its absolute 

 force ; that is, its force, supposing its ve- 

 locity equal to its weight : for its moving 

 or acting force maybe greater or less, ac- 

 cording as its velocity is increased or di- 

 minished, in respect of that of the weight. 

 As, for example, if a man be the power, 

 and can raise from the ground a certain 

 weight, that weight will express or be 

 equal to the intensity of the power ; for in 

 this case, whatever engine be made i^se 

 of, that part of the engine, where the 

 weight is duly applied, will move just as 

 fast as that on which a man acts with his 

 whole force. A power may act in any 

 direction whatever; but a weight has 

 only one direction, viz. towards the cen- 

 tre'of the eai-th. 



When we speak of the mechanical 

 powers, the word power is taken in a ve- 

 ry different sense from that above laid 

 down ; since, in this case, it signifies only 

 an organ or instrument, whereby a power 

 of a known intensity is made to act upon, 

 a weight; and, therefore, we must take 

 care not to attribute any real force to any 

 simple or compound machine, as many 

 are apt to do, merely because the name 

 power has been given to mechanical or- 

 gans, not from their effect, but from the 

 effect which the power produces by their 

 means. For how much soever the force 

 of a power is thereby increased, in order 

 to sustain or raise a weight far superior 

 to it in intensity, yet this cannot, be done 

 without losing in space and time what is 

 gained in force ; contrary to what some 

 have vainly imagined, because the vulgar 

 commonly speak of a machine as they do 

 of an animal ; attributing that effect to the 

 machine, which is only the effect of the 

 power by means of the machine : thus, it 

 is usual to say, such a machine raises such 

 a quantity of watei-, or performs such and 

 such work ; when we should say, if we 

 would speak philosophically, such a run- 

 ning stream, such a iall of water, the 

 wind, or so many men, horses, oxen, &c. 

 raise so much water in such a time, &c. 

 by means of such or such a machine. It 



