CHAPIEE VI. 



THE MINERAL KINGDOM. 

 MATTER FORMATION OF CRYSTALS POLARISATICW, ISO, 



our mea o re search through organic nature 

 we met with an endless variety of beautiful 

 and instructive materials for the employment 

 of the microscope. If we now turn our atten- 

 tion to the inorganic or mineral kingdom we 

 shall find a vast storehouse filled with objects 

 of unsurpassed interest to the microscopist. 

 In the examination of the many beautiful 

 forms presented to us in the phenomena of crystallisation, 

 and the study of the varied chemical combinations, the 

 student will discover a never-ending source of useful occu- 

 pation. 



We are as yet in great ignorance of the manner ilk 

 which the majority of crystals belonging to the mineral 

 kingdom are formed : we know, however, that very few can 

 be reproduced by the chemist. But, although ignorant of 

 the means whereby the great majority of crystals have 

 been formed in the vast laboratory of nature, we can 

 crystallise an immense number of substances, watch their 

 numerous intricate modes of formation, and that in the. 

 smallest appreciable quantities, when aided by the micro- 

 scope. Among natural crystals those employed in the 

 formation of rocks open up a wide field to our view. The 

 varieties of granites present us with the earliest crystal- 

 lised condition of the earth's crust as it cooled down, the 

 structure of which is beautifully exhibited under polarised 

 light. Plate VIII. No. 160, is a section of a granlm 



