IV.] SNOW AND ICE. 59 



were, in fact, nothing but water which had been congealed 

 by so intense a cold that it was impossible to thaw it. 

 And the Greek word for ice {Kpv<TTa\Xoc, kriistallos), thus 

 suggested our term crystal. Even at the present day many 

 crystallised minerals are vulgarly called •' congealed water." 

 The substance which has just been noted as having given rise 

 to the word " crystal " is known as rock-crystal, and must be 

 familiar to most readers, since it is used by the jeweller for 

 working into ornamental objects, and by the optician for the 

 manufacture of those spectacle lenses which are said to be 

 made of " pebbles." The term " crystal " is now applied 

 to all symmetrical solid shapes assumed spontaneously by 

 lifeless matter. 



Rock-crystal is sometimes found in crystals of gigantic 

 size ; at other times in excessively small specimens. This 

 seems to show that the same species or kind of matter may 

 assume forms unlimited in size. A few years ago some 

 enormous specimens of dark-coloured rock-crystal were 

 found in cavities of a rock above the Tiefen Glacier in 

 Switzerland ; one crystal, christened the " Grandfather," 

 weighing as much as 276 lbs., and another, called the 

 " King," weighing 255 lbs. Yet this same substance may 

 be obtained in crystals so minute as to be seen only with 

 aid of a microscope. Such great variation of size in the 

 same kind of crystalline matter has no parallel among living 

 bodies. It is true that certain animals and plants, placed 

 under very favourable conditions, may increase beyond their 

 average size, but this increase is confined within compara- 

 tively narrow limits. A crystal, however, has absolutely no 

 limit to its growth \ it increases in size by addition of matter 

 from the outside, and as long as new matter is thus presented 

 to it, so long will it continue to enlarge. A small crystal of 

 alum, for example, suspended in a saturated solution of the 



