GRANITE 731 



GONIOMETER. An instrument employed to measure the angles of crystals. 

 The most perfect instrument is the reflecting goniometer of Wollaston. The angle of 

 the crystal is measured by determining through what angular space the crystal must 

 1)6 turned so that two rays reflected from two surfaces successively shall have the same 

 direction. A simpler form of the instrument consists merely of a semicircular gradu- 

 ated scale of degrees with a moveable and a fixed radius. It is a most important in- 

 strument to the scientific mineralogist. 



GOOSEBERRY. The fruit of the Eibes grossularia, a plant belonging to the 

 natural order Bibesiacees or Grossulariacees. 



GOOSEBERRY-GARNET. A name for Grossularia. See GARNET. 



GOSIiARITE. Native hydrous sulphate of zinc, named from its occurrence in 

 the Kammelsberg mine, near Goslar, in the Hartz. 



GOSSAN, a Cornish mining term. An oxide of iron, mixed with other matters. 

 Gossans are found on the upper portions of lodes, and according to their characters 

 are regarded by the miners as favourable or unfavourable indications. The gossans 

 are probably the result of the slow decomposition of the sulphate of iron from the 

 fluid in which the metalliferous matter, deposited in the lode, has been precipitated, 

 or of the sulphides which may have been previously formed. The gossans are fre- 

 quently very rich in silver, and sometimes they contain gold. 



GOSSYPIU1VX. The cotton-tree. See COTTON. 



GOUI.ARD LOTION or WATER. A solution of the acetate of lead. See 

 LEAD, ACETATE or. 



GOURDS. The hard integument of the fruit of several species of cucurbitaceous 

 plants, used in the East for vessels, musical instruments, &c. See CALABASH. 



GOVERNOR. A mechanical arrangement, usually attributed to Watt, for regu- 

 lating the motion of a steam-engine. 



GRADUATOR. A vessel employed in vinegar-manufacture. See ACETIC 

 ACID. 



GRAINS OF PARADISE. The fruit of several zingiberaceous plants ; some- 

 times it is called Mallaguetta pepper. Pereira distinguishes between the two ; but it 

 appears that they commonly pass for the same in commerce. Grains of paradise are 

 imported in casks, barrels, and puncheons from the coast of Guinea. They are used 

 to give a factitious strength and pungency to beer and cordials. 



By 56 Geo. III. c. 58, no brewer or dealer in beer shall have in his possession or 

 use grains of paradise, under .a penalty of 200^. for each offence: and no druggist shall 

 sell it to a brewer under a penalty of 500. for each offence. 



GRAIN TIN. The purest kind of metallic tin. See TIN. 



GRAIKCMATITE. A variety of Tremolite. See HORNBLENDE. 



GRANITE, in the common and original acceptation of the term, denotes a rock, 

 composed of felspar, quartz, and mica. It oftentimes contains, in addition to these, 

 some other minerals. 



These component minerals of granite, both essential and accidental, are united 

 together by a confused crystallisation, not only mutually penetrating and interfering 

 with each other, but sometimes the small crystals of one are completely enveloped in 

 the large crystals of a different kind of mineral, and it is a very common occurrence 

 for one or even more of these minerals to be developed in large crystals, in a granular 

 basis of the whole, so as to constitute a porphyritic granite. This character is gene- 

 rally imparted by the felspar, and rarely by the quartz or mica. Boose. 



The chemical composition of ordinary granite is generally as follows: 



Silica 72-3 



Alumina tts.v.0--' . . , ''..- ' . 15-3 



Alkalis JtfD*:^ . fr ."-: . . ' ' , a : 7'4 



Lime, magnesia and iron __ , . . <-^- 5-0 



This rock consists generally of about 40 per cent, of felspar, 30 or 40 per cent, of 

 quartz, and from 10 to 20 per cent, of mica. 



The granites of Cornwall and Devonshire have been long celebrated for their ex- 

 ceeding durability. Sir Henry de la Beche thus describes the situation of the work- 

 able granites : 



' There is much good granite on Dartmoor, though it is not always sufficiently 

 accessible to be carried long distances : the chief places where it is worked in large 

 quantities and afterwards exported are, Hey or High Tor on the east, and near King 

 Tor on the west. The granite from the former place is conveyed by a tram-road to 

 the Stover canal, down which it is carried in boats, and afterwards down the Teign 

 to Teignmouth, to be shipped for its destination. That from the west side of the 

 moor is conveyed by the Prince's Town and Plymouth tram-road to the latter place 

 and shipped. 



