XV111 PREFACE. 



and a visit, on my way home through Switzerland, to 

 the Valorsine, where I had an opportunity of verify- 

 ing the observations of M. Necker on the granite 

 veins and altered stratified rocks of that district. I 

 may also mention the time occupied in the correction 

 of the second edition of the first and second volumes, 

 and the delivery of a course of Lectures in May and 

 June, 1832, at King's College, London, on which 

 occasion I had an opportunity of communicating to 

 the scientific world a great part of the views now 

 explained in my last volume. 



London, April, 1833. 



