HI 



ONOXOV. 



GOLD. 



given, or under ny other definition which accurately characterises 

 Tbeognu and other*. Brunck'* edition contain* aUo a collection of 

 llnonuo from the comic writer*. 



The Gnomic writer* are sometime* all classed under the general 

 name of Elegiae poet*. [Ettor.] 



IKON (the Greek yniu**), or style of a dial, is the plate which 

 project* from the surface of the dial-plate, the etlgu of it* ahade deter- 

 mining the hour-line. The plates now in use being flat, the gnomon 

 is in the plane uf the meridian, and Its sloping edge forms an angle 

 with the horizon equal to the latitude of the place, and U consequently 

 parallel to the axis of the earth. No sensible error is made by con- 

 founding the edge of the gnomon with the earth's axis ; but in lunar 

 dials a sensible error would arise, except in places of which the latitude 

 is nearly 90 : this error, in cither cam, depends upon the parallax of 

 the luminous body, and the position of the dial-plate. The ancienU, 

 who tued hemispherical dial-plates, placed the radius which threw the 

 shade in the direction of the north pole-star, and therefore the hour- 

 linen wore circular arcs, at regular intervals of 16. Herodotus says 

 (ii. 109) that the Greeks borrowed the gnomon and the sphere (ruAoi) 

 from the Babylonians. 



The science of gnomonics, upon which many formal treatises have 

 been written, has declined as the theory of astronomy has advanced 

 towards correctness. In the succeeding article one method of construc- 

 tion of a dial will be briefly explained. It is not worth while to 

 enter upon the details of constructions which are now of no use. 

 A sun-dial may be sufficiently well adjusted to give the time within 

 a few minutes, provided the observer has an almanac, or some other 

 work in which the equation of time is contained, by which the 

 indications of the sun are made to agree with those of the clock. 

 DIAL.] 



GNOMONIC PROJECTION. The gnomonic projection of any 

 portion of a sphere U that which is constructed on the supposition 

 that the eye is in the centre of the sphere. The consequence is, that 

 any great circle whatsoever of the sphere is projected into a straight 

 line ; which property can belong to no other projection. 



The most convenient method of projecting the whole sphere 

 gnomonically is to imagine a cube inscribed about it, on each face of 

 which one-sixth part of the sphere is projected, by lines drawn through 

 the centre. The maps of the earth and of the stars published by the 

 Society for the Diffusion of Useful Knowledge are drawn in this 

 manner, a full account of which may be found in the ' Explanation of 

 the Maps of the Stars' (Baldwin, 1836). The result is six maps, 

 which embrace the whole sphere ; the shortest distance from any one 

 point to another on the sphere being projected into the shortest 

 distance between their corresponding points on the map, when they 

 lie on the same map. 



The gnomonic projection derives its name from the connection 

 between the methods of describing it and those for the construction of 

 a gnomon or dial. The direction in which the shadow of a line 

 parallel to the axis of the earth will be thrown is the intersection of 

 the hour circle for the time being with the surface of the dial (whether 

 plane or not). Imagine a sphere, and the surface of the dial drawn 

 through its centre. Upon this sphere describe the heavens, and 

 project the whole upon a circumscribed cube. Nothing is more easy 

 than to draw the hour circle upon such a projection, and if the inter- 

 section of the surface of the dial with the cube be traced out upon the 

 cube, the points at which the projections of the hour circles meet the 

 intersection of the cube and the dial ore those towards which the 

 shadow of the axis will point at the hour in question. When a dial is 

 to be constructed geometrically, this is the most simple plan : but 

 calculation, as in other instances, is superior to construction for 

 purposes of accuracy. 



^TK -, .l.-nved from the Greek word gnotit (yr&aa), " know- 

 ledge," was employed by the fathers of the first two centuries as a 

 generic term to designate all individuals who professed to interpret 

 the Scriptures by the aid of philosophy. It is supposed from - 

 passages in the New Testament (Col. ii. 8 ; 1 Tim. i. 4 ; vi. 20 ; 2 Tim. 

 ii. 16, 17; Titus, iii. 9; 1 John, ii. 18) that the doctrines of the 

 * were taught in the times of the Apoetles ; and the Nicolaitans, 

 who are condemned by St. John (Kev. ii. 6, 15), are looked upon by the 

 fathers as forming a sect of the Gnostics. Many of the fathers con- 

 sidered Simon Magus, Dositheus, and Menander to be the first 

 individuals who propagated Gnostic opinions ; but they are more 

 correctly classed by others among the opponents rather than the 

 oorrupters of Christianity. The principal teachers of Gnosticism wi-re 

 SatuniiniiK. Basilides, Cerinthtis, Carpocrates, and Prodicus, of whom 

 the most celebrated were C'erinthus and Carpocrates ; and some of 

 their tciieU were held on the authority of passages in the apocryphal 

 K'-IH-I. of the New Testament. Irenam* (' Adv. Hroren.' iii. 11) state* 

 that St John wrote his gospel in order to refute nUnm ; 



iny critics reject this testimony of Ireueos, and maintain that 

 Cerinthus lived in the second century. The Ebionitos akto [EIIIOMTEH] 

 are supposed to hare been Gnostic*. 



The origin of the Gnostic syitem has been traced to various sources. 



Some have derived their doctrines from the Alexandrian school of 



philosophy; other* from the Jewish Cabbala [CABBALA]; and a still 



. number from the Oriental belief in two great independent 



principles, one the author of good, and the other of evil. Many parts 



of the Gnostic syitem may be alleged in favour of each of these sup- 

 positions; but it seems to be forgotten that Gnosticism is in 

 generic term, and that it included many *ect* that differed consider- 

 ably from each other : we should therefore regard it rather as derived 

 from all these ancient systems than formed from any one in particular. 

 For the reasons that have already been mentioned, it is difficult to give 

 an account of their opinions that will apply equally to all the sects into 

 which the Gnostics were divided ; but the following abstract contains 

 the doctrines which were regarded by the father* as characteristic of 

 Gnosticism. 



One of the chief sections considered it beneath the might of the 

 Supreme Deity to labour, and therefore maintained that God could 

 not have created the world. They believed that God dwelt in a 

 jjfruma (wkripaiut) of inaccessible light, and that he was unknown to 

 the world before the coming of Christ ; that he created two other 

 beings, called Jioni, or emanations ; that from these other AMTU were 

 descended, at the head of whom was one named Demiuryiu, who created 

 the world ; that this Demiurgus was the God of the Old Testament ; 

 that Christ, who was one of the .(Eons, was sent into the worl.l to 

 restore men to the yttotit (knowledge) of the true God ; that the Xxm 

 Christ descended into the man Jesus at his baptism, and left him when 

 he was led to crucifixion, so that the man Jesus alone suffered. This 

 was in effect the belief of the Gnostics of the Jewish Alexandrian 

 school. Another branch, probably of previous oriental converts opposed 

 to Judaism, maintained that the Demiurgus was entirely antai.- 

 to the Supreme Deity, and that this was shown in the Old Test. 

 that all matter was intrinsically evil ; that the incarnation of 

 was undertaken to relieve mankind from this position ; and that an 

 individual at his death was raised to inhabit the divine plcroma, into 

 which corruptible and sinful matter could not > 



Their doctrines are said to have produced very opposite effects upon 

 their moral conduct ; some, looking upon the body as sinful, mor- 

 tified it by severe penances ; while others, with the same opinion, led 

 immoral lives, maintaining that the soul could not be affected by the 

 acts of the body. 



(Neander, Kircliengetckichtt ; Mosheim, Kcdaiattical Jfutory ; 

 Lardiier's Ifitlory of Heretic* ; Mohler, Vermeil vber den Urtprung der 

 (inottiker, 1831 ; Baur, Die Chrittlichen Gnotit I'M getchichlliche ntui<:k- 

 elung, 1835.) 



GOITRE. [BBONCHOCELE.] 



GOLD (Au) is a metal which has been known from the remotest 

 antiquity, and has been universally employed as a medium of exchange. 

 Although the quantity of gold which is found, when compared with 

 that of other metals, is small, yet it occurs in greater or less abundance 

 in almost every part of the globe. It occurs in the native state, and 

 alloyed with silver, also occasionally combined with tellurium, and 

 frequently mixed with metallic sulphurets and arseniurets. It is 

 indeed stated by Oahn that but little sulphuret of iron is met with 

 which does not contain some gold. A large quantity of goM is 

 obtained from South America ; the richest mines of Europe are those 

 in Hungary ; it has been found also in the sand of the Rhone, the 

 Rhine, and the Danube ; small quantities are occasionally found in the 

 stream tin-works of Cornwall ; and in Wicklow in Ireland, and the 

 lead-hills of Scotland, no inconsiderable portions have been from tinu> 

 to time collected. But by far the largest supplies of this metal are 

 now derived from Australia and California. Gold is also met with in 

 tolerably large quantity in the Uralian mountains of Siberia. 



Native gold occurs crystallised, capillary, and massive ; the primary 

 form is a cube. It gives no cleavage ; fracture hackly ; hardness 2'5 

 to 3-0; colour yellow, of various shades; streak shining, opaque; 

 specific gravity 17 to 19. 



Gold not unfrequently occurs alloyed with silver, and this compound, 

 where the quantity of silver is considerable, is known by the name of 

 di'ctrum. Klectrum analysed by Klaproth was found to consist of 64 

 of gold and 36 of silver, which are almost exactly in the proportions of 

 one equivalent of each metal. Boussingault, who has since examined 

 electrum from various parts of Columbia, found it to consist of very 

 different proportions of the melals, but they were all definite compounds. 

 Gold is separated from the various substances with which it is mixed 

 by the process of amalgamation ; this consists in combining it with 

 mercury, and heating the amalgam formed, so as to distil the mercury, 

 which is thus repeatedly used for the same purpose. 



Cold is of a fine yellow colour, and is susceptible of a high degree of 

 polish. It is nearly as soft as lead ; its specific gravity is 19'3 ; it is so 

 exceedingly malleable that one grain may be extended o\ 

 square inches of surface, and gold leaf is only about E ^, of an inch 

 in thickness ; some authors say fjjj^ of an inch. Gold is also exceed- 

 ingly ductile; a single grain maybe drawn out into 500 feet of wire : 

 in point of tenacity it is* inferior to iron, copper, platinum, and silver ; 

 a wire 0'787 of a line in diameter is capable of supporting about 150 

 pounds. Gold suffers no change by exposure to air or moisture, even 

 when heated. It melts at about 2016 Kahr., according to Darnell's 

 pyrometer ; when in fusion it appears of a brilliant green colour. It 

 is scarcely at all volatile, and may bo long kept in fusion in a furnace 

 without losing weight ; but when it is melted by the heat of a lens a 

 plate of silver held over it at some inches distance becomes gilt by its 

 vapour. It contract* more than any other metal on cooling, and crys- 

 tallises in octahedrons. 



