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PREFACE. 
and a visit, on my way home through Switzerland, to 
the Valors ine, where I had an opportunity of verify- 
ing the observations of M. Neeker 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. 
