601 



POLARIZATION OF LIGHT. 



POLICE. 



603 



tution becomes _i- - JL + 2 ( C -2!L? + ESLfN !-' . Equating 

 PS* FX* \ PS* PN" ) PN> 



these values of P <J* and leaving out terms which destroy each other, 



1 cos. 1 e 1 cos. 2 V , sin. 9 sin. 9 1 , 



we have _ = ; whence - = ; ,and 



PS* PS* PX* PN rs 2 PN' 



sin. 8 : sin. <f : : P s ! : P x 2 . 



Now, produce Q p till it meets x 8, produced, if necessary, in T ; and 

 draw s A parallel to N P : then, by trigonometry, 



s A : p s : : sin. APS: sin. PAS:: sin. Q p s : sin. Q p N ; that is, 



B A : P S : : sin. : sin. 8' ; hence 



SA : PS : : PS* : PN 1 , which being compounded with the identical 

 proportion PS:PX::PS:PN gives 



s A : P N : : p s 3 : P x 3 . 



But s A being parallel to p x, s A : p N : : s T : N T ; therefore 

 8 T : N T : : P s 3 : P x 3 . 



Thus the ratio of s T to N T is known ; and, consequently the position 

 of the tangent p T, from the given position of p. If the poles x and s 

 are unlike, as above supposed, the curves are of the kind called con- 

 vergent, as x p s ; but if the poles are similar, the curves will be 

 divergent, as x p" s'. 



POLARIZATION OF LIGHT, 1 . , , , . .. , . 



POLARIZATION, MOVEABLE, I ""* * ound - at the end of 



POLARIZED RINGS, J 



POLDERS. The meadow lands by the side of rivers, or of the 

 sea-shore, which are only protected from inundation by means of 

 enclosure dykes, banks, or walls, are known on the Continent by the 

 name of Polders ; and in Holland, where these hydraulic works are the 

 most common, they are further subdivided into the schorres, the 

 maritime polders, the boezem landen, and the drained lakes. The 

 various works connected with these modifications of polders will be 

 discussed under RIVER ENGINEERING, and SEA DEFENCES. For the 

 present, it may suffice to say that the polders almost invariably require 

 a complete enclosure, with an interior collecting drain for the land 

 waters, which are discharged directly through sluices, or outfall gates, 

 or are lifted over the bank by windmills or other mechanical means. 

 The polders are, generally speaking, used as grazing land for horned 

 cattle, or at tunes for the growth of rape or other oleaginous grains : 

 of course the cattle are withdrawn from them during the winter 

 months. The superintendence of the works for the defence and main- 

 tenance of the polders in North- Western Europe is entrusted to local 

 administrations, or syndicates, acting under the control of the respective 

 departments of public works in the countries where those polders 

 exist. 



POLE. [PEBCH.] 



POLE, POLAR. The word iro'\os as applied to a point means a 

 turning or hinge point, and was applied to the points at the extremity 

 of the axis of the celestial sphere in the ancient astronomy. Hence, 

 on the hypothesis of the earth's rotation, it comes to mean the 

 extremities of the axis on which the earth turns. From this primary 

 meaning all the various uses of the word pole have been derived. 

 For example, when it was found that the magnet did not always point 

 to the north pole, but to another point, it was natural to call that 

 other point the magnetic pole. Previously to this use of the word, it had 

 already taken a wider signification, as follows : On looking at the 

 position of the equator with respect to the poles, it is obvious that if 

 the equator, or circle of equal day and night, should be changed, the 

 axis must also be changed, and the poles of rotation. Hence any great 

 circle of the sphere is said to have its poles, meaning those points 

 which would become poles of rotation if that circle became the 

 equator. [SPHERE.] 



A term seldom passes through several significations, however nearly 

 related, without at last becoming generic in the widest sense. The 

 word pole is now used to denote any point which is of so strik- 

 ing a character as to require a distinct name. In physics the word 

 is naturalised in magnetism, electricity, and optics; insomuch that 

 any tendency towards a particular point, or even towards a particular 

 direction, is termed polarity. In geometry, the only definition which 

 can now be given of this term is, that it means any point which it is 

 wanted to mean. Thus a point considered as the origin of Co- 

 OUDIXATES is called the pole; and when distances measured from the 

 origin are among the co-ordinates, they are called polar. Again, it is 

 a well known property of the conic sections, that if all possible chords 

 be drawn through any one given point, and a pair of tangents be 

 drawn from the extremities of each chord, the intersections of all the 

 pain will lie in one straight line ; the point through which the chords 

 are drawn is called the pole of that straight line. 



POLE STAR. [URSA MINOR.] 



POLEMARCH. [ARCIION.] 



POLICE is that department of government which has for its object 

 to secure the safety, peace, and convenience of the community. We 

 have here to do with this its primary object, namely, the prevention of 

 crime and the pursuit of offenders ; but besides this the police system 

 is subservient to other purposes, such as the suppression of mendicancy, 

 the preservation of order in great thoroughfares, the removal of 

 obstructions and nuisances, and the enforcing of those local and general 



laws which relate to the public health and comfort. [MUNICIPAL 

 CORPORATIOXS.] 



In the Anglo-Saxon times the whole community was called upon to 

 aid in protecting life and property ; and the spirit of this system, 

 though the system ia no longer applicable to the existing state of 

 society, still characterises this department of our institutions. The 

 object of the present notice will be to give some account of the former 

 and present constitution of the police in England. 



In the Anglo-Saxon period the sheriff of each county, chosen by the 

 freeholders in the folkmote, was the chief officer responsible for the 

 conservation of the peace ; and in his half-yearly visitations to each 

 hundred in the county, he inquired whether there was any relaxation 

 in the efficiency of the means in use for this object. The hundred 

 originally consisted of ten divisions, each containing ten freeholders, 

 mutually pledged to repress delinquencies within their district. All 

 males above the age of twelve were obliged to appear at the sheriff's 

 visitation, to state the district to which they belonged, and to be sworn 

 to keep the peace. One out of every ten freeholders had precedency 

 of his companions, and the whole were bound to bring delinquents to 

 justice within thirty days on pain of being themselves liable to 

 penalties. The population was thinly scattered ; every man was known 

 to his neighbours ; no man could depart from his dwelling without 

 the consent of his fellow-pledges ; and the consent of the sheriff was 

 necessary to enable a man legally to go out of his own county. No 

 man could enter a neighbourhood without being recognised as a 

 stranger, and probably exciting suspicion ; and this suspicion, 

 quickened by the responsibility of the freeholders, soon caused a hue 

 and cry if the stranger could give no good account of himself. [HuE 

 AXD CRT.] 



After the Conquest, the advantages of the system were recognised 

 by several of the Norman kings, particularly by William I., and by 

 Henry I. in the early part of his reign. The former ordered that every 

 freeman should be under pledges, and the latter that views of frank 

 pledge should be taken in order that none might escape responsibility. 

 But a great innovation was made in the Anglo-Saxon system when 

 the sheriff, instead of being elected by the freeholders, was appointed 

 directly by the king. Doubtless he would generally be a Norman, and 

 therefore indisposed to meet the people in their popular courts : at all 

 events the sheriff's " tourn," or half-yearly visitation, came in no long 

 tune to be neglected. 



When, Henry I. instituted the office of justices-itinerant [CoxSER- 

 VATORS OF THE PEACE], the functions of the sheriff became of still 

 less importance. By the stat. Merton, c. 10, passed 20th Henry III. 

 (1236), freemen who owed suit to the county or hundred court were 

 allowed to appear by attorney. The stat. Marl. cc. 10 and 25 passed in the 

 52 Henry III. (1268), dispensed with the attendance of the baronage 

 and clergy at the sheriff's court unless their attendance was specially 

 required ; and it also prohibited the justices-itinerant from amercing 

 townships on account of persons above the age of twelve years not 

 having been sworn in pledges for keeping the peace. By these various 

 measures the ancient system was greatly impaired ; and the new laws 

 which were introduced from time to time for the purpose of repressing 

 crime do not seem to have been very successful. In 1277, nine years 

 after the passing of the statute of Marlebridge, the absence of " quick 

 and fresh pursuit " of felons is noticed as an evil which was increasing. 

 To supply the energy and alacrity of the old system, fines and penalties 

 were imposed by the stat. Westminster, prim. 3 Edward I., sec. 9, on 

 all who neglected to pursue offenders. The statute directs tliat " all 

 generally be ready and apparelled at the commandment and summons 

 of the sheriffs, and at the cry of the county, to pursue and arrest any 

 felons when any need is." The statute of Winchester, 13 Edward I. 

 (1285), endeavoured to maintain the spirit of the Anglo-Saxon laws by 

 making the county or hundred responsible in case of a delinquent not 

 being forthcoming, and the duty of apprehending him was cast upon 

 all the king's subjects. This statute also regulated the office of con- 

 stable, an officer who had succeeded the Anglo-Saxon hundred or 

 tything-man. [CONSTABLE.] The constables were directed what 

 measures they were to take for preventing crime and keeping the peace. 

 In every town, village, and tything they were to set a watoh according 

 to the size of the place, every night from Ascension till Michaelmas, 

 from sunset to sunrise ; and the watchmen were to apprehend and 

 examine all strangers, and on their refusal to obey the summons of the 

 watchmen, they might levy hue and cry to take them. The gates of 

 ail walled towns were to be shut from sunset to sunrise : the highways 

 were to be kept clear of bushes, woods, or dykes for the space of two 

 hundred feet from hedge to hedge, so that felons might not conceal 

 themselves. Every man was to have arms in his house for preserving 

 the peace ; and the constables were empowered to take the view of 

 such arms. The prevention of crime, as well as the pursuit of 

 criminals, was also one of the primary duties of constables, and they 

 were charged to make presentment at the assizes, sessions of 

 the peace, or leet, of all blood-sheddings, affrays, outcries, rescues, 

 and other offences against the peace. The justices to whom these 

 presentments were made hi the first instance, reported directly to 

 the justices-itinerant, or at once to the king or his privy-council; 

 and the supreme executive made provisions accordingly. At the same 

 time the responsibility cast upon the hundred quickened the vigilance 

 of the inhabitante ; and this responsibility extended to individuals hi 



