r l 





A/.IMI'TH IUAI.. 



to distinguish by specific tann with respect to any motion or other 

 phenomenon, U called the axis. Thus we hart axe. of co-ordinates, of 

 oicilUliun. of inertia, of rotation, of polarisation, Ac., under which 

 head, definition, will he Rh 



The word, when ued by iUelf, generally mean, either axis of /Jo/o- 

 lio*, or axi* of Sifmmrtry. An axis of rotation, or revolution, is the 

 line about which a body turn. ; an axis of symmetry in a line on both 

 aide* of which the part, of the body are disposed in the same manner, 

 ao that to whatever distance it extend* in one direction from the axis, 

 it extend* a. far in the direction exactly opposite. Or if perpendiculars 

 to the axi. be drawn from all points and in all directions 'through the 

 body, the whole of each perpendicular which is within the limit* of the 

 body will be buectod by the axis. Such is the middle line of a cone, 

 any diameter of a sphere, the line drawn through the middle of the 

 opposite face, of a cube, Ac. 



AX1.K. Since the extensive use of locomotives, the theory of the 

 action of axles, and the causes of their fr\<-turo, have been subject* of 

 elaborate inquiry among engineers. Whether solid or hollow axles, 

 with a given weight of metal, are the stronger, U one among these 

 inquiries. Mr. Yorke, in a paper read before the Institute of Civil 

 Engineers in 1S43, contends for the superior strength of hollow axles ; 

 but this conclusion is disputed by others. The theory of axles may, 

 indeed, be considered at present in a tentative tftate ; meanwhile, patents 

 are frequently obtained for improvement* in form and in mechanical 

 action. Hardy's patent axles have shown the possession of such a 

 remarkable degree of toughness, that the Privy Council in 1849 granted 

 a continuation of the patent ; and remarks were made in the House of 

 Lords relating to the lning of railway accidents by their use. Since 

 that period the patent has been sold for a considerable sum to a 

 company at Birmingham, established for the manufacture of these 

 axles on a large scale. 



Rowan's patent axles are intended to lessen the amount of friction 

 usually produced by the action of a wheel on its axle. For the axle in 

 common use is substituted a small centre revolving arm, along which 

 are fitted five or six rollers, closed at each end ; the sheath over the 

 rollers revolves with very little friction, as it touches upon a small 

 portion only of each of the rollers. The arm is turned truly parallel, 

 with a bevelled shoulder to fit a corresponding bevel on the rollers ; 

 and a screw-nut is fitted in the extremity of the arm, having also a 

 bevelled shoulder. The rollers are fitted into and carried by two rings 

 in such a manner that they are perfectly free to move on their centres ; 

 and, when placed on the arm, are free also to move round it without 

 lateral motion, being confined by the bevels. By this contrivance the 

 bearing is transferred to the surfaces of the rollers, and does not affect 

 their centres. 



Mr. Bessemer, in a ' Treatise on Railway Axles,' considers the pro- 

 bable causes why the axles of railway carriages break more frequently 

 than those of a road vehicle, in spite of the fact that the one go 

 upon smooth rails, while the other pass over roughly paved surfaces. 

 He attributes it to the oscillation of a railway carriage. The flanges of 

 the two wheel, are alternately driven up close against the rails by this 

 oscillation, and whenever this occurs, there is a momentary tendency 

 in one wheel to revolve a little faster than the other ; and thus a strain 

 or twist is given to the axle, first in one direction and then in the 

 other. This straining may take place five thousand times in an hour 

 in a railway carriage in rapid motion ; and Hr. Bessemer conjectures, 

 that the iron of the axle may in this way be thrown into a molecular 

 state liable to fracture. To obviate this source of mischief, he pro- 

 pose, the use of a compound axle, formed of two pieces so united 

 endwise that, while the ordinary action of an axlo is maintained, the 

 two halves may yield a little during oscillation, instead of being 

 subjected to a twist in the fibre of the metal. 



AYKKX AKIiKKY, properly Ayin-i-Akbari, is the title of a geogra- 

 phical and statistical account of the Mogul empire in India during the 

 reign of the emperor JeUUeddin-Mohammed-Akbor, written by his vizir 

 Abu'l Fail. [Aeri. FAZL and AKBAR. in Bioo. Div.J It constitutes 

 the third or concluding part of the ' Akbamamen ' of the same 

 author. The first volume consists of a summary account of Akbar'a 

 ancestor!, and the second volume comprises the occurrences of his 

 reign, from his secession to the throne down to the 47th year. A free 

 and often abridged translation of this work into English was under- 

 taken by Mr. Francis OUdwin, and a portion was issued in Calcutta as 

 arlya.1783. It has more than once been reprinted in England. As 

 an original and we may say an official account of the internal 

 organisation of the Mogul empire at the time of its greatest prosperity, 

 the ' Aytn-i-Akbari ' is highly interesting. It is divided into four parts : 

 the flnt three are chiefly political and legislative ; the fourth part is 

 chiefly statistical and geographical, giving a description of the several 

 provinces at that time comprehended under the Mogul government, 

 and a detailed account of the ancient institutions, religion, and litera- 

 ture of the Hindoos, which U very comprehensive, and in many parts 

 sarprUngly accurate. 



AYUNTAMIENTO, JUSTICIA, CONCEJO, CABILDO, REGI- 

 .re the namm given in Spain to the councils of the towns 

 and villages. These councils are in general composed of the corregidor 

 alcalde, r*0dora, jurados, and penoneroi, or hoinbres-buenos. All 

 these officer., with the exception of the corregidor, who was always 

 appointed by th government, were originally elected every year by 



he inhabitants of the concejo or commune. To be the head of a 

 'unity, a native of Spain, and settled in the commune, were the only 

 qualification, required either from an elector or a candidate. The origin 

 of this institution may be traced to the remotest period of Spanish 

 listory. (Maadeu's ' Historia Critics,' vola. iv. to ix., more particularly 

 vol. viii. book 3.) It has been ever the most cherished and the most 

 carefully preserved of all their privilege* by the Spanish people. It 

 was chiefly by the ayuntamientos that the resistance to the French 

 under Buonaparte was rendered so persevering and so obstinate ; and 

 it was the law against them in 1840, which created so much diimti. 

 Faction in the country as enabled Espartero to succeed in exiling the 

 regent-queen Christina, (For a full account of them, aee Mariana, 

 ' Examen de la Antigua Legulacion de Espafia ; ' ' ReconiUcion de las 

 Leyes de estos Reinos/ book vii. ; Mariana, ' Historia de Espafia,' book 

 xx. chap. 13,) 



AXADIKINK. An alkaloid of uncertain composition, found in the 



I I in A.'iilimchta. 



A'ZIMUTH, a corrupted Arabic word, which when properly written 

 is at-oaml, the at being the article at, assimilated to the initial letter of 

 the word to which it is prefixed ; aimt means ' a way, a road, a path ; ' 

 also ' a part, tract, country, or quarter.' 



Azimuth denotes the angular distance of the horizontal point which 

 is directly under a star from the north point of the horizon. Thus if 



s be the spectator, z his zenith, z N his meridian, N A the horizon, and 

 7. A the vertical circle passing through a star *, then the angle A s N is 

 the star's azimuth, or it is the angle made by the vertical circle z A and 

 the meridian z s. 



The only instruments in use by which the azimuth could be imme- 

 diately observed are the theodolite and the altitude and azimuth circle. 

 [THEODOLITE ; CIRCLE.] It is not one of those elements which are 

 usually measured in astronomy. When the star is known (that is, 

 when its declination is known), the azimuth can be found by observing 

 the altitude A * and solving a spherical triangle ; for in the triangle 

 whose sides are the complements of the star's altitude, the star's decli- 

 nation, and the latitude of the place, the azimuth is the angle opposite 

 to the complement of the declination, as may be seen in the triangle 

 z P *, where P is the pole. Similarly the latitude of the place may be 

 found when the altitude and azimuth of a known star are observed at 

 the same moment. For in the triangle just mentioned, z * and * P are 

 given, and the angle * z p ; whence z P may be calculated. When the 

 azimuth of a star is found by means of an instrument adjusted by the 

 magnetic needle, then the azimuth obtained (which needs a correction 

 on account of the deviation of the needle) is termed the magnetic 

 azimuth. In this way the deviation of the needle may be found at any 

 known place by observing the magnetic azimuth and calculating the 

 true azimuth by observing the altitude of a star in the manner before 

 described. 



An instrument is said to be moved in azimuth when it is turned on a 

 vertical axis, so that any line in it drawn through the axis point* to 

 the same altitude in the heavens, but not to the same azimuth. Simi- 

 larly an instrument is moved in altitude when it is turned on a horizontal 

 axis. An altitude and azimuth instrument is one which admits of both 

 motions. 



It is hardly necessary to observe that when the star is in the horizon, 

 and when the azimuth is less than 90, (90 azimuth) is the amplitude 

 (which see) ; and that when the azimuth is greater than 90, (azimuth 

 90) is the amplitude. 



An azimuth circle is a circle all the points of which have the same 

 azimuth, that is, a vertical circle. For azimuth Compass, see COMPASS. 



AZIMUTH or ANALEMMATIC DIAL is one whose plane is 

 parallel to the horizon, and whose gnomon, or stile, is moveable in a 

 vertical position. The hour-point* are in the periphery of an ellipse, 



XII. 



as vi, xti, vi, of which let o be the centre ; and the foot of the stile 

 moves in a north and south line,** MX, which is graduated from o to M 



