THE TECHNOLOGIST. [May 1, 1864 



436 ON GRANITE AND ITS USES. 



kind of grain larger than the others. Any one may be in crystals many 

 inches, or even feet in length. In 172o, a cave opened at Zinkehberg, 

 on the Grimsel, contained five tons of crystal, among which were 

 column-;, clear as water, from 500 to 800 lbs. In 1770, in Hagdorn, near 

 Fischbaeh, a column weighing 14 cwt, one S cwt., and one 6 cwt., were 

 found, of the greatest purity. 



As for the shape of the grains, they are generally squeezed together 

 in the rock, which was once probably liquid. But they often shoot into 

 crystals, that is, solids with plane or flat sides or faces, bounded or 

 circumscribed by definite angles. Rock-crystal or quartz appears as a 

 six-sided prism and pyramid ; mica as a rhomboid, solid or with six 

 lozenge faces ; felspar occurs as an oblique prism. 



Rock-crystal is the characteristic ingredient of glass ; felspar, the 

 characteristic source of the constituent of earthenware and porcelain ; 

 mica is of much less importance. 



Rock-crystal is called also silica, from the Latin word for a flint, 

 which has the same composition as quartz. It is known as a crystalline 

 solid ; as a white, glistering, gritty powder, and as a soft impalpable 

 one. An intense heat melts it, but no heat can volatilise it, and it is 

 insoluble in all ordinary fluids. It consists of oxygen, and a com- 

 bustible body, in some respects like charcoal, in others like a metal, 

 called silicon or silicium. 



A beautiful and most interesting dej^artment of technology is con- 

 nected with rock-crystal, as one of the precious stones or gems. It is 

 the chief element of glass, and the largest constituent of porcelain, and 

 we shall look at it again in its relation to these ; but before we consider 

 it as transformed by man in the course of his industrial doings into 

 marvellous things, it must be looked at in connection with an art which 

 perhaps some may be jealous of hearing called utilitarian. Rock-crystal 

 is one of the precious stones or gems, and is pre-eminent among them in 

 a tlixeeford way — 1. It is itself ranked among ' the stones most precious.' 

 2. It is the chief ingredient of many of those most highly prized which 

 contain other things besides itself. 3. It is associated with the larger 

 number of the gems as these are with granite. I wish to refer specially 

 to the precious stones, that, in connection with them as famous and 

 familiar things, I may dispose of two weighty objections to technology, 

 and may urge an important argument in defence of its study and 

 practice. 



Mankind in all ages have looked upon those few minerals, which 

 they have called precious stones, gems, or jewels, with delight and 

 wonder. Their origin has been ascribed to supernatural causes, and 

 they have been invested with the most mysterious powers. They covdd 

 render their wearer invisible ; they could banish drunkenness (especially 

 the amethyst), cure madness, and make certain the passionate love of 

 those who were objects of affection. They could detect poison, and were 

 its best antidotes ; they could heal, indeed, all diseases. In darkness 



