74 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



physiological changes which have taken place in them since their 

 first formation. The ardent glow of the Sunstone and the pale 

 watery gleam of the Moonstone, no less than the lovely play of 

 azure tints in Labrador-spar and the bronzy sheen of Paulite, are 

 the result of physiological processes [taking place in crystals which 

 were originally clear and translucent. In the profound laboratories 

 of our earth's crust slow physical and chemical operations, resulting 

 from the interaction between the crystal, with its wonderful mole- 

 cular structure, and the external agencies which environ it, have 

 given rise to new structures, too minute, it may be, to be traced by 

 our microscopes, but capable of so playing with the light-waves as 

 to startle us with new beauties, and to add another to 



" The fairy tales of science, and the long results of time." 



Yes ! minerals all have a life-history, one which is in part 

 determined by their original constitution, and in part by the long series 

 of slowly varying conditions to which they have since been subjected. 

 In spite of the circumstance that their cycles of change have 

 extended over periods measured by millions of years, the nature of 

 their metamorphoses and the processes by which these have been 

 brought about are, in all essential respects, analogous to those which 

 take place in a Sequoia or a butterfly. In spite, too, of the 

 limitations placed upon us by our brief existence on the globe, it is 

 ours to follow in all its complicated sequence this procession of 

 events, to discover the delicate organization in which they originate, 

 to determine the varied conditions by which they have been con- 

 trolled, and to assign to each of them the part which it has played 

 in the wonderful history of our globe during the countless ages of 

 the past. 



The subject of Distribution, or Chorology, is one of no less import- 

 ance in the study of the mineral than in that of the vegetable and 

 animal kingdoms. The relations of minerals to one another, and 

 the manner in which they make their appearance in respect both to 

 time and place, constitute a most instructive and suggestive field of 

 research. 



The older mineralogists paid some attention to the question of the 

 mode of association of minerals with one another, which they 

 described under the term " Paragenesis." But this was at a time 

 when only large and freely c^stallized specimens received much 

 attention. At the present day this question of the varied distri- 



