i«o 9 — 1842] VOYAGE 27 



formed a marked feature in the geography of the globe. Letter 7 

 The geology of these mountains pleased me in one respect ; 

 when reading Lyell, it had always struck me that if the 

 crust of the world goes on changing in a circle, there ought 

 to be somewhere found formations which, having the age 

 of the great European Secondary beds, should possess the 

 structure of Tertiary rocks or those formed amidst islands 

 and in limited basins. Now the alternations of lava and 

 coarse sediment which form the upper parts of the Andes, 

 correspond exactly to what would accumulate under such 

 circumstances. In consequence of this, I can only very 

 roughly separate into three divisions the varying strata 

 (perhaps 8,000 ft. thick) which compose these mountains. 

 1 am afraid you will tell me to learn my A B C to know 

 quartz from feldspar before I indulge in such speculations. 

 I lately got hold of a report on M. Dessalines D'Orbigny's 

 labours in S. America; 1 I experienced rather a debasing 

 degree of vexation to find he has described the Geology 

 of the Pampas, and that I have had some hard riding for 

 nothing, it was however gratifying that my conclusions 

 are the same, as far as I can collect, with his results. It 

 is also capital that the whole of Bolivia will be described. 

 I hope to be able to connect his geology of that country 

 with mine of Chili. After leaving Copiapo, we touched at 

 Iquique. I visited but do not quite understand the position 

 of the nitrate of soda beds. Here in Peru, from the state 

 of anarchy, I can make no expedition. 



I hear from home, that my brother is going to send me a 

 box with books, and a letter from you. It is very unfortunate 

 that I cannot receive this before we reach Sydney, even if 

 it ever gels safely so far. I shall not have another opportunity 

 for many months of again writing to you. Will you have 

 the charity to send me one more letter (as soon as this 

 reaches you) directed to the C. of Good Hope. Your letters 

 besides affording me the greatest delight always give me 

 a fresh stimulus for exertion. Excuse this geological prosy 

 letter, and farewell till you hear from me at Sydney, and 

 see me in the autumn of 1836. 



1 Voyage dans PAmerique Miridionale, etc. (A. Dessalines D'Orbigny). 



