NATURE OF THE MATERIALS IN THE LITHOSPHERE 25 



fire," allow each to be attacked by the powerful reagent, hydro- 

 fluoric acid. The common glass under the attack of the acid 

 remains as it was before, a sphere, but with shrunken dimensions. 

 The crystal, on the other hand, is able to control the action of the 

 solvent, and in so doing its individuality is again revealed in a 

 beautifully etched figure having many curving outlines it is as 

 though the crystal had possessed a soul which under this trial has 

 been revealed. This glimpse into the nature of the crystal, so as 

 to reveal its structural beauty, is still more surprising when the 

 crystal is taken from the acid in the 

 early stages of the action and held 

 close beneath the eye. Now the lit- 

 tle etchings upon the surface display 

 each the individuality of the sub- 

 stance, and joining with their neigh- 

 bors they send out a beautifully 

 symmetrical and entirely character- 

 istic picture (Fig. 11). 



The lithosphere a complex of 

 interlocking crystals. To the lay- 

 man the crystal is something rare FIG. n. " Light figure" seen upon 



and expensive, to be obtained from an etched surface of a crystal of 



a jeweler or to be seen displayed in ^^ (after Goldschmid t and 

 the show cases of the great muse- 

 ums. Yet the one most striking quality of the lithosphere which 

 separates it from the hydrosphere and the atmosphere is its crys- 

 talline structure, a structure belonging also to the meteorite, and 

 with little doubt to all the planets of the earth group. A snowflake 

 caught during its fall from the sky reveals all the delicate tracery 

 of crystal boundary; collected from a thick layer lying upon the 

 ground, it appears as an intricate aggregate of broken fragments 

 more or less firmly cemented together. And so it is of the litho- 

 sphere, for the myriads of individuals are either the ruins of former 

 crystals, or they are grown together in such a manner that crystal 

 facets had no opportunity to develop. 



Such mineral individuals as once possessed the crystal form may 

 have been broken and their surfaces ground away by mutual attri- 

 tion under the rhythmic beating of the waves upon a shore or in 

 the continuous rolling of pebbles on a stream bed, until as bat- 



