66 THE COMING [CH. 



task of presenting his views in a popular form would 

 be aided by his having to expound them to a miscel- 

 laneous audience. For two years, these lectures 

 were delivered, and attracted much attention ; the 

 favourable impressions produced by them on a man of 

 the world have been recorded by Abraham Hay ward, 

 and on more scientific thinkers by Harriet Martineau. 



The third volume of the Principles was not 

 completed till a second edition of the second volume 

 had been issued. This third volume, appearing in 

 May 1833, dealt with the classification of the Tertiary 

 strata, to which Lyell had devoted so much labour, 

 studying conchology under Deshayes, and visiting all 

 the chief Tertiary deposits of Europe for the collec- 

 tion of materials. The application of the principles 

 enunciated in the two earlier volumes to the un- 

 ravelling of the past history of the globe, constituted 

 the chief task undertaken in this part of the great 

 work. But not a few controversial questions were 

 dealt with, and the famous 'metamorphic theory' 

 was advanced in opposition to the Wernerian hypo- 

 thesis of 'primitive formations.' The volume was 

 appropriately dedicated to Murchison, who had been 

 Lyell's companion in the famous Auvergne excursion, 

 which had produced such an effect on his mind. 



Within a twelvemonth, a third edition of the 

 whole work in four small volumes was issued, and in 

 the end no less than twelve editions of the Principles 



