16 OUTI.INT.s HI MILD-GEOLOGY PARTI 



which deal with the architecture of the globe, mineralogy 

 becomes .\ singularly fascinating study. I shall have 

 occasion in later ch allude to some of its attrac- 



tions. Should the observer be led from the minerals to 



ivestigation of the rocks among which they 1 

 will find himself in presence of some of the most ir 

 ing problems in geology. Some of these crystalline rocks 

 are amongst the oldest of the globe ; their origin is linked 

 with the earth's early history, they are witnesses of 

 the power of that internal heat which has play 

 notable a part in the growth of the solid land. As a rule, 

 too, the districts where they occur are more rugged than 

 those which the fossiliferous formations overspread : hence 

 they may present everywhere crags, knobs, and bosses 

 of rock, as well as the more continuous sections of water- 

 courses. By these frequent exposures the successive 

 bands of rock can be traced ; their variations in 

 breadth, in composition and in mineral contents can 

 be followed; and their intercalations, curvatures, frac- 

 tures, and veins, can be unravelled, so as to reveal, 

 more or less clearly, the structural plan of a whole 

 region. 



In most places, save on the face of precipices and 

 steep declivities, the rocks which form the framework of 

 a country are more or less concealed by various super- 

 ficial accumulations. Even should he never set himself 

 to the study of the underlying formations, the observer 

 may find ample scope for inquiry in these upper deposits. 

 In one region he will encounter thick masses of earth or 

 loam, containing here and there the bones of long extinct 

 mammals. In another quarter he may meet with sheets 



