But when he came to indicate a possible method by which one species might be derived from another, he was less happy in his suggestions. He recognised the value of the evidence derived from the study of the races which have arisen among domestic animals, and from the crossing of different forms. But his main argument was derived from the acknowledged fact that use or disuse may cause the development or the partial atrophy of organs--the case of the 'blacksmith's arm.' Unfortunately some of the suggestions made by Lamarck, in this connexion--like that of the elongation of the giraffe's neck to enable it to browse on high trees--were of a kind that made them very susceptible to ridicule. His theory was of course dependent on the admission that acquired characters were transmitted from parents to children, and in the absence of any suggestion of 'selection,' it did not appeal strongly to thinkers on this question. Lyell first became acquainted with the writings of Lamarck in 1827. As he was returning from the Oxford circuit for the last time--having now resolved to give up law and devote himself to geological work exclusively--he wrote to his friend Mantell as follows:-- 'I devoured Lamarck _en voyage_.... His theories delighted me more than any novel I ever read, and much in the same way, for they address themselves to the imagination, at least of geologists who know the mighty inferences which would be deducible were they established by observations. But though I admire even his flights, and feel none of the _odium theologicum_ which some modern writers in this country have visited him with, I confess I read him rather as I hear an advocate on the wrong side, to know what can be made of the case in good hands. I am glad he has been courageous enough and logical enough to admit that his argument, if pushed as far as it must go, if worth anything, would prove that men may have come from the Ourang-Outang. But after all, what changes species may really undergo! How impossible will it be to distinguish and lay down a line, beyond which some of the so-called extinct species have never passed into recent ones. That the earth is quite as old as he supposes, has long been my creed, and I will try before six months are over to convert the readers of the _Quarterly_ to that heterodox opinion[87].' Lyell was at that time at work on his review for the _Quarterly_ of Scrope's _Central France_, and was also completing the 'first sketch' of the _Principles_. But it is evident that as the result of continued study of Lamarck's book, Lyell found it, in spite of its fascination, to embody a theory which he could not but regard as unsound and not calculated to prove a solution of the great mystery of evolution. Accordingly when the second volume of the _Principles_ was issued in 1832, it was found to contain in its opening chapters a very trenchant criticism of Lamarck's theory.