60S 



POSTING. 



POTASSIUM. 



666 



carrying mails and by the penny postage system than in Ireland." In 

 1784 there were posts six days a week on only four lines of road; 

 letters to all other places being conveyed only twice or thrice a week. 

 Now there are daily posts to almost every village, and there is but one 

 important town that has not two daily mails both with London and 

 Dublin. In 1784 the whole expense of the office in Ireland was 

 1 5,000^., including salaries of provincial postmasters and the conveyance 

 of mails. Out of this sum, 55001. only was allotted to the provinces ; the 

 sum allotted in 1856 for the like service was 134,0002., divided thus : 

 conveyance of mails by railways, 65,5051. ; by coaches and cars, 

 27,1682. ; by foot-messengers, 10,3342. ; and salaries and wages paid in 

 provincial offices, 31,1222. In 1829 the cost of conveying the mail by 

 mail-coaches was nearly four times the average rate of England ; this 

 excess has now disappeared, and in 1859 the average rate per mile was 

 for England 2d., for Scotland 2J</., and for Ireland 2d. 



The same paper pays a just tribute to the exertions of Mr. Biauconi 

 for the improvement of intercommunication in Ireland, particularly in 

 reference to the transmission of letters. 



The amount of postage collected at different towns in the United 

 Kingdom (including the postage-stamps sold by the Post-Office and by 

 the Board of Inland Revenue) shows some curious results. London, 

 of course, through which passes nearly one-half of the total corre- 

 spondence of the kingdom, attains a great predominance, the amount in 

 1857 being 833,9522. ; Liverpool, with 255,000 inhabitants, contributed 

 104,8652.; while Manchester, with 316,000 inhabitants, only contri- 

 buted 89,7652. ; and Birmingham, with 232,000 inhabitants, but 42,1 071. 

 Bristol, with about 100,000 inhabitants (including Bedmineter), fur- 

 nished 31,2641. ; Leeds, with 172,000 inhabitants, only 23,8442. ; and 

 Sheffield, with 135,000 inhabitants, no more than 16,5652. In Ireland 

 the contributions were more in accordance with the size of the towns : 

 Dublin contributed 60,3912.; Belfast, 15,5472.; Cork, 11,9152.; and 

 Limerick, 71151. In Scotland : Edinburgh, with 160,000 inhabitants, 

 contributed 59,1772.; and Glasgow, with 358,000 inhabitants, only 

 68,8772. It must be recollected, however, that in many cases some 

 towns are used as a sort of depot, from whence postage-stamps are dis- 

 tributed over a wider district than others. 



POSTING, from the French "poste," derived from the Low Latin 

 word " posta " (Ducange, in i-erbo), is BO called from horses being placed 

 at certain stations or posts, where they may be hired by individuals at 

 their pleasure. The application of the words " post " and " postmaster " 

 as well to the transmission of letters and the persons to whom this 

 business is entrusted, aa to stations where post-horses are kept, and the 

 persons who own or have the care of them, is the cause of much con- 

 fusion : and it frequently cannot be understood in reference to which 

 branch early writers intend these terms to be applied. The ambiguity 

 is not confined to the English language. Post-horses were first esta- 

 blished by the governments on the continent of Europe in the 13th and 

 1 4th centuries' for the conveyance of despatches ; they were occasion- 

 ally employed for the conveyance of persons connected with such 

 governments, and gradually by passengers in general. Posting con- 

 tinues in most countries to be- carried on by the state, which retains 

 the monopoly of supplying post-horses, and usually of forwarding mails 

 and diligences. The prices are fixed by the governments, as well as 

 the number of horses that must be employed, according to the weight 

 or number of persons to be conveyed, or even by the state of the 

 rood*. In the United States and British North America there is at 

 present (1859) no posting, at least in the sense in which the term is 

 commonly used ; that is to say, a person cannot have his carriage con- 

 veyed in such a direction as he may wish, and hire fresh horses at 

 convenient stages. He must engage an " extra exclusive " in some 

 principal town, and the same horses must convey him throughout his 

 whole journey, unless another large town should lie on the road. This 

 is the mode of travelling known on the Continent by the name 01 

 " vetturino," " voiturier," or " Lohnkutscher." The want of the power 

 of posting is not so inconvenient as might be supposed, for the number 

 of private carriages is not large, and in districts where there is much 

 travelling, communication is usually facilitated by steam-boats, railways 

 and stage-coaches. 



Posting is very generally established in England, but is now less 

 used in consequence of the introduction of railways. In frequented 

 and populous districts, change of horses may commonly be procured al 

 intervals of from eight to twelve miles, and in the most remote anc 

 thinly inhabited at inns not more than from fifteen to twenty miles 

 apart. The trade is wholly in the hands of private speculators. The 

 rate of travelling with post-horses varies according to the weight of the 

 carriage and the number of horses employed ; from eight to nine miles 

 an hour may be stated as the average rate of a pah- of horses under 

 ordinary circumstances. The number of horses hired depends solely 

 on the will and discretion of the party hiring, which are controlled bj 

 no legal regulation whatsoever. The payment is estimated per mile 

 for each pair of horses, without reference to the number of persons 

 conveyed, and a second pair of horses is charged at the same rate as the 

 first ; the payment to the postmaster does not include the driver, who 

 expects a gratuity of about three-pence a mile. Four horses is the 

 greatest number ever required for one carriage. Sixteen or eighteen 

 pence per mile is the usual price for each pair of horses, and when the 

 payment of postboys and turnpikes is added, a journey will be foun< 

 to cost about twenty-two pence a mile. If a post-chaise or fly be 



required as well as post-horses, no additional charge is made ou account 

 of the carriage. Post-chaises are now almost things of the past ; but 

 lys with a single horse are to be had at most towns, and all large inns, 

 at about la. a mile. The price of posting is nearly uniform throughout 

 England, but there is considerable variation in the degree of goodness 

 of the horses and chaises provided. On much-frequented roads, where 

 ,here is generally competition in the posting trade, the accommodation 

 s very superior to what is found at little-frequented inns, where an 

 nferior description of post-horse is kept, which is often insufficiently 

 'ed because it is not frequently employed. A postmaster pays yearly for 

 one horse and carriage, 72. 10s. ; for two, 122. 10s. ; increasing with the 

 number, for a licence to let post-horses. 



POSTULATE (pustulatum, atTtj^a), a thing required to be granted, 

 or the use of which in reasoning is demanded. 



The distinction between a postulate and an axiom lies in this that 

 the latter is admitted to be self-evident; while the former may be 

 agreed upon between two reasoners and admitted by both, but not as 

 a proposition which it would be impossible to deny. The distinction 

 above made is really necessary ; for example, writers on the evidences 

 of Christianity assume the existence and attributes of the Creator as 

 postulates : they take them for granted. A person who is in the habit 

 :>f not distinguishing the senses to which the words postulate aud axiom 

 have been affixed above, might say they assume the existence and 

 attributes above mentioned as axioms, by which another person might 

 understand things necessarily indisputable ; while the writers them- 

 selves only mean by the assumption, that what they take for granted 

 lias been previously proved by writers on natural theology ; or, at any 

 rate, that until they are admitted, the question of the evidences cannot 

 be entered upon. The confusion which prevails as to the use of the 

 word axiom would be lessened by the introduction and proper use of 

 the word postulate, which is our reason for adding these few words to 

 what has been said under AXIOM. 



POTASH. [POTASSIUM.] 



POTASH ALUM. [ALUM.] 



POTASSA. [POTASSIUM.] 



POTASSIUM (K). This metal was discovered in 1807 by Sir 

 Humphry Davy. Most of its compounds had been known for years 

 prior to that date, and that the basis of them was a metal, that they 

 were in fact compounds of a metallic oxide, had long been suspected. 

 In that year, however, Davy succeeded in isolating the metal by sub- 

 mitting fused hydrate of potash to the action of a powerful voltaic 

 battery. Potassium has since been obtained by more facile methods, 

 and the following is the one now generally adopted. 



Crude bitartrate of potash (argol) is heated in a covered iron pot till 

 gases cease to be evolved. The product a mixture of carbonate of 

 potash and finely divided carbon is triturated in a mortar, while still 

 hot, with some coarsely powdered charcoal, and the porous mass 

 promptly transferred to an iron mercury bottle, or other wrought-iron 

 retort. A neck is formed to the bottle or retort by simply screwing 

 into the mouth a piece of iron tube about six inches long, and the 

 whole is then so imbedded in a furnace- as that the open end shall 

 project about a quarter of an inch through an opening in that side of 

 the furnace that is purposely formed of plate iron. The fire is now 

 lighted and fed with a mixture of coke and charcoal ; an intense white 

 heat is thus produced, and vapours of potassium soon appear at the 

 mouth of the apparatus, and burn with a brilliant purple flame. A 

 receiver is now fitted on, the construction of which needs some care ; 

 it may be so formed that the potassium shall drop into naphtha the 

 moment it solidifies ; or it may merely be an iron box five inches wide, 

 twelve long, and a quarter of an inch deep, formed by clamping 

 together two very shallow wrought-iron dishes made of plate-iron one- 

 sixth of an inch in thickness. In either case an opening must be made 

 exactly opposite the neck of the bottle, in order to allow of the latter 

 being cleared by a stout steel wire in the event of its becoming stopped 

 up by condensed potassium, &c. ; such an opening also allows of the 

 escape of the carbonic oxide gas that is abundantly evolved during the 

 process. The receiver must be kept cool by ice, or other convenient 

 means, aud, in the case of the flat box, must, at the close of the 

 operation, be plunged under the surface of rectified Persian naphtha, 

 as otherwise the potassium would quickly become oxidised. The 

 metal thus obtained is not pure, and must be redistilled in a similarly 

 arranged apparatus. 



The manufacture of potassium is a somewhat dangerous operation, 

 owing to the frequent formation of explosive compounds. The 

 apparatus in which it has been performed should be immersed in water 

 an soon as cold, for a black detonating compound soon forms by 

 exposure of the residual potassium to the air, and explodes by the 

 slightest friction. 



The decomposition that takes place during the manufacture of 

 potassium is primarily a simple case of deoxidation, as expressed in 

 the following equation : 



KO, C0 a -f 



C, = 



SCO 



Carbon. 



Carbonic 

 acid. 



Unfortunately, however, the liberated potassium has a great ten 

 dency to unite with carbonic oxide, and form a very explosive com- 



