ni 



F.CH; 



KCHO. 



781 



til* Church, from iU being than appointed to be read in churches. A 

 Syriao and an Arabic version are extant. The Latin version, which 

 is supposed to be of the firat century, contain* numerous words adopted 

 from the Greek, but differs much from the prevent Greek text 



(Kftlaiatinu, or At Boot of At CTUrrf, by Luke Howard, F.R.S.. 

 1827; Dalrymple, Lord Haflem. Wadom of Solomon, or Ecdttiatticu, 

 1765; Soontag. Commnt. de Jen, Sineida Bcdttiattieo, 4to., 1792; 



Soontag. 



BreUchneider, de lib. Jom Sineidir (prolegom. pp. 10-32), dates the 

 original compilation 180 B.C. ; Home'* htroduet to Ike Kbit, vol. ir.) 



E'CHKVIN, the name given under the old French monarchy to the 

 municipal magistrate* of various titie* and towns. At Paris there 

 were four cchevins and a prdvot des marchands, whose jurisdiction 

 extended over the town and adjacent territory ; in the other town* 

 there was a maire and two or more eohevins. In the south of France 

 the same officers were called by other names, such as consuls in 

 Languedoc and Dauphine, capitouls at Toulouse, jurats at Bordeaux. 

 The last name, that of jurats, is retained in some of the English 

 municipalities. They tried minor suits, laid the local duties or octroi 

 ni-.ji imports, had the inspection of the commercial revenues and ex- 

 !"!!. liture, as well as the superintendence of the streets, roads, and 

 markets, the repairs of public buildings, Ac. The name echevins aeems 

 to hare been derived from scabini, a Latin word of the middle ages, 

 which was used in Italy under the Longobards, and in France, Flanders, 

 and other countries under the Carlovingian dynasty. In Holland they 

 are called schepens. The acabini were the assessors to the counts or 

 missi dominici, appointed by the monarch to administer a province or 

 district ; and they were chosen among the local inhabitants. After- 

 wards, when charters were given to the communes, the municipal magis- 

 trate* elected by the burgesses assumed also the name of scabini or 

 cchevins. (Ducange, ' Glossarium.') 



ECHO. (4x*^> 4x<>*> KMatd). When sonorous undulations are pro- 

 pagated from any origin through the elastic medium of the air, the 

 spherical wave-like surface then conveys the sound through the cir- 

 cumjacent space, and moves from its origin and centre with a velocity 

 of about 1125 feet in a second, at the ordinary atmospheric pressure 

 and temperature ; for the velocity of undulations propagated through 

 elastic media depends only on their indices of elasticity and not on 

 their intensity. [ACOUSTICS.] 



Suppose the point o to be the origin of a sound which in its pro- 

 great encounters a plane obstacle KM ; if this plane be sufficiently 

 extended, a point M may be easily found which the sound will have 

 just reached at the end of a given time. The waves which have pre- 

 viously reached the nearer points A,B, c, being precluded from 

 advancing, are there reflected according to the usual law of reflection 

 of light, that is, new spherical undulations nab, b'bc, c'cd are generated 

 from A, B, c as centres, and their radii at the moment we have spoken 

 of are respectively A& = OM OA, BC=OM OB, crf=on oc, and it is 

 easily seen that all these spherical surfaces originating from A up to M 

 and existing simultaneously, may be exactly enveloped by a single 

 j.irii.m of a spherical surface of which the centre is placed in a 

 (xwition B corresponding to o in respect to its distance from N M, but 

 at the opposite side of the obstacle ; this spherical surface, of which 

 the radius is B M, is the true returning wave at that moment, and 



being impressed on the auditory organs, so as to be distinguished from 

 the original sound, is called the teko. 



When a sound originate* at a point o, and is reflected by a plane 

 obstacle A o, the reflected pulsation of the air occupies the space of a 

 conical frustum o A c e, the vertex of the cone B being situated sym- 

 metrically with o at the opposite side of A o. In order that a person 

 may hear the echo of his own sounds, it is therefore necessary that 

 his situation may be a point o' in a perpendicular to A o ; and that a 

 second person may hear the echo of the voice of another at o, he must 

 be situated in the frustum a A oc, so that the angles of incidence and 

 reflection of the sound which reaches his ear may be equal, as in the 

 case of the reflection of light, and the impact of perfectly elastic bodie* 

 [LlOHT ; COLLISION] ; in both cases the distance from A c must be 

 sufficiently great to distinguish between the original and the reflected 

 sound. 



The echo of a continued sound or note may be heard in the 

 inverse order of time to that in which it was generated, provided 

 the origin of the sound moves more rapidly towards the hearer than 

 the rate at which sound travels. Thus a flash of lightning moving 

 towards a person will produce a roll of thunder which, echoed by 

 clouds, will be heard as it were backwards ; but if the direction of the 

 flash be such that the points of its course are nearly equidistant from 

 the auditor, an instantaneous and intensely loud clap will be substi- 

 tuted for a continued roll. 



The murmuring sound produced by the discharge of great guns is 

 the succession of echoes from the particles of vapour floating in the 

 atmosphere, and when the discharge U effected under a dense cl>>ucl, 

 the echoes are stronger and better reflected, and a noise resembling a 

 thunder-roll may then be heard. The whizzing of a bullet is attributed 

 to its impinging in a state of rapid rotation on particles of vapour. 



The time intervening between the primitive sound and its echo has 

 sometimes been employed in determining the distance from the 

 observer to the reflecting object, allowing 571 feet for each intermediate 

 second of time ; but like all methods dependent more on individual 

 judgment than mechanical measurement, this process must be liable 

 to considerable irregularities. 



When several objects reflect sound, the number of echoes is greatly 

 multiplied, not only from the primary echoes of each, but also from 

 secondary and tertiary echoes by second and third reflections of re- 

 turning waves against the reverberatory obstacles ; each re-echo consists 

 of only portions or frusta of the preceding ; their intensities tin 

 diminish, and they gradually die away upon the ear, in the same 

 manner that the images become obscure and by degrees imperceptible 

 in consequence of the diminution of light when we look between t\v<> 

 opposite and parallel plane mirrors. The reflecting plane, however, 

 must be at a great distance in order to produce polysyllabic echoes. 

 At Woodstock is one repeating from seventeen to twenty syllables, and 

 the Swiss mountaineers sing their Jtanz del Vaehtt, so that the echoes 

 form an accompaniment to the tune itself. 



The first echo heard in such circumstances is by no means neces- 

 sarily the loudest. Taking any ellipse of which one focus U the 

 origin of the sound and the other the place of the auditor, it is a well- 

 known property of this curve that right lines drawn from the foci to 

 any point in it moke equal angles with the tangent at that point. Con- 

 ceive now this ellipse to rotate round the line joining the foci so as to 

 form a prolate spheroid, then sound emanating from one focus and 

 reflected by a portion of the surface will be directed after reflect 

 the other, and its intensity will depend on the solid angle subtended at 

 the focus by the reflecting body. Each echoing body may be con- 

 ceived as a portion of such a spheroidal surface, taking a large axis 

 major to comprehend the more distant bodies ; and since the sum of 

 the solid angles subtended by the more distant reflectors may be 

 greater than those given by the nearer, the echo produced by them, 

 though not reaching the ear so soon as that of the nearer, may, under 

 such circumstances, be louder. We must, however, bear in mind in 

 our estimate that this intensity has a source of diminution in the 

 increase of distance. This case frequently occurs in places encom- 

 passed by chains of mountains, as at Killarney and the Welsh lakes, &c. 



When the succession of echoes from several bodies is suffiY 

 rapid, a continued sound or note may be produced, though the original 

 sound was merely momentary ; and when not sufficiently rapid for 

 this purpose, a clamorous noise is produced, and hence Echo with IHT 

 thousand tongues and babbling propensities has furnished matt, r for 

 poetic imagination from Ovid to Shakspere. Hence, Echo has been 

 called the" shadow of a sound," " a voice without a mouth, and words 

 without a tongue." Echo too, though represented as a female, never 

 speaks until she is spoken to, and at every repetition of what she has 

 heard, continues to make it less, an example recommended to the 

 special imitation of scandal-mongers. As a single ha / may be con- 

 verted into an imitation of a stunning laugh, the romantic and echoing 

 regions inhabited by the Scandinavian races materially assisted their 

 untutored imaginations in attributing this appalling music to the 

 aerial revelries of invisible hags or witches. The blow of a hammer 

 against one side of a parallel fissure in a rock, sometimes produces 

 echoes sufficiently rapid? in succession to give the tone of a bell, as in 

 the Bell-rock at Tanbridge-wi'llx. 



But when, as in the case of tin- .!.-. nic fluid, the original cause of 

 Hound may be said to exist simultaneously through an extensive tract 

 of an excited atmosphere, a sound perfectly continuous and majestic is 

 produced in the thunder-roll, which may frequently be heard again 



