G L 



r 



needle-like points, or aiguilles, 

 which characterize granite moun- 

 tains, are usually rounded. It 

 has been remarked, with much 

 truth, that abruptly conical hills 

 are characteristic of the formation 

 which Humbolt designates as 

 gneiss-granite. Pew of the primary 

 rocks are so metalliferous as gneiss. 

 Its ores occur both in beds and 

 veins : more frequently in the 

 latter. 



GOLD. (Sax.) A metal, when pure, 

 of a rich yellow colour : specific 

 gravity 19-3. It does not readily 

 combine with oxygen ; hence it 

 does not rust when exposed to the 

 air, and it may be melted and re- 

 melted frequently with scarcely 

 any diminution of its quantity. : It 

 is said to have been kept in a state 

 of fusion for nearly eight months 

 without undergoing any perceptible 

 change. In ductility and mallea- 

 bility it surpasses all other metals, 

 and it may be beaten into leaves so 

 exceedingly thin, that one grain of 

 gold shall cover fifty-six square 

 inches, such leaves having the 

 thickness only of one 282,000th 

 part of an inch. Its tenacity is 

 inferior to that of iron, copper, 

 platinum, and silver. Gold is solu- 

 ble in nitre-muriatic acid, and in a 

 solution of chlorine. The gold 

 coins of this country contain one- 

 twelfth part of copper alloy : jew- 

 eller's gold is a mixture of gold and 

 copper, in the proportions of three- 

 fourths of pure gold and one-fourth 

 of copper. 



GONI'ATITES. A sub-genus of am- 

 monites, in which the last whorl 

 covers the spire. Seven species 

 have been found in the carbonifer- 

 ous system, and seventeen in the 

 primary strata. 



GONIO'METER. (from ^wvta, an angle, 

 and fierpov, a measure, Gr.) An 

 instrument invented by M. Caran- 

 geau, for the accurate measurement 

 of crystals. Dr. Wollaston also 



8 ] G N 



invented a goniometer called the 

 reflecting goniometer ; this is a very 

 superior instrument. There are 

 two kinds of goniometers, the plain 

 and the reflecting. Of the latter 

 Mr. Phillips says, " in almost every 

 instance in which I have tried it 

 upon the planes produced by good 

 fractures, the success has been com- 

 plete. The great value of this in- 

 strument, which may be used with 

 readiness and ease, demands the 

 attention of every one who has the 

 slightest pretension to crytallo- 

 graphical research. The reflecting 

 goniometer is of great use to the 

 geologist, as well as to the miner- 

 alogist. He finds those rocks which 

 are termed primary, and many of 

 those which are called transition, 

 to consist, not of one homogenous 

 mass, but of two or more minerals, 

 so intermixed and associated that a 

 reference to the chemist is of little 

 avail to him : by such means he 

 may indeed become informed 

 whether a particular earth or alkali 

 is to be found in the mass, but the 

 various substances of which it is 

 compounded are often too minute, 

 and therefore too intimately associ- 

 ated with the others, to allow of a 

 determination as to which of the 

 component substances may contain 

 the earth or the alkali so discovered. 

 Hence structure, if it exist, becomes 

 a character of essential importance, 

 for it will be found that fragments 

 far too minute for analysis will 

 often afford brilliant planes, well 

 adapted to the use of the reflecting 

 goniometer. 



The surfaces produced by cleav- 

 age are sometimes very small, and 

 therefore are not adapted to the 

 common goniometer ; while for the 

 reflecting goniometer, it matters 

 not if the surface be small, provided 

 it be perfect and brilliant ; a sur- 

 face of the 100th part of an inch in 

 length and breath will suffice. 

 GONYLE'PTES. A genus of the second 



