198 Notes on Natural History in India. [Sess, 



against the slightest approach to idolatry. All the same, Bishop 

 Heber's ' Travels in India ' is the most interesting book which 

 has ever been written on that country, and I would advise every 

 one to read it. The only man of greater genius who has 

 written on India is Colonel Sleeman; but his books are addressed 

 to the Anglo-Indian resident, not to one who has never seen 

 the country. 



To return to Science, — India is made up geologically of four 

 great provinces, very unlike each other: (1.) The southern 

 volcanic table-land, of which the most common rock is basalt, 

 often capped with laterite. Below the basalt lies stratified 

 sandstone, and still lower, granite ; but these are only ex- 

 posed in a few places. (2.) The great alluvial plains along 

 the courses of the Indus and the Ganges. This is not the 

 largest division, but it is by far the richest and most important, 

 and when people talk of India, it is generally the Indus or 

 Ganges valleys they are thinking of. All the common descrip- 

 tions of India are only true of these great alluvial plains. (3.) 

 The waterless district of Eajpootana, a barren wilderness of sand. 

 (4.) The Himalayan mountains, of crystalline schists, limestone, 

 and granite. These mountains are inhabited nearly up to the 

 snow-line, which on the southern face, where the air is moist, 

 is about 13,000 feet above the sea. On the northern face, 

 where the air is dry, perpetual snow is not found till you ascend 

 to nearly 16,000 feet. This is the very reverse of what one 

 would at first thought expect. It seems strange that the south 

 aspect, turned to the equator, should be colder than the north 

 aspect, turned away from the equator. But the amount of 

 snow is determined more by the amount of moisture than by 

 the temperature. The south face is always the moist one, owing 

 to the hot winds blowing up from the plains. Not only does 

 more snow fall on the south side in winter, but less melts in 

 summer. Another peculiarity of the Himalayas is, that the 

 lower hills are generally well wooded on the north face, but 

 bare and sterile on the south face. This is owing partly to 

 the fierce winds blowing up from the plains, but partly also 

 to the continual changes of temperature killing plants. On the 

 north face, the climate is much less variable. We have thus 

 four regions : 1st, The basalt table-land ; 2d, The alluvial 

 plains; 3d, The Eajpootana desert; and 4th, The Himalayan 



