102 The Cambrian and 



of matter. While soaring into this elevated region, he 

 caught a glimpse of those views respecting the distinction 

 between physical ond chemical atoms, from the development 

 of which Dumas has since derived so much celebrity. 



On the other hand, in his latter work, dedicated to the 

 relief of human suffering, he has abstained as much as pos- 

 sible from such speculations, and has evinced an exemplary 

 caution in confining his practical deductions strictly within 

 their legitimate limits, at the same time that he has dis- 

 played a profound sagacity in the discrimination and treat- 

 ment of the diseases which fell within his province. 



The Cambrian and Silurian Discussion. 



In the fifty-second volume of this Journal we inserted, at 

 p >ge 305, from the Literary Gazette, Professor Sedgwick's 

 classification of the Palaeozoic Rocks, in which he describes 

 the position and extent of the Cambrian and Silurian groups 

 of that great series. Sir R. I. Murchison, in a letter to the 

 Literary Gazette, inscribed at page 355 of the same volume 

 (fifty-second volume) of this Journal, objects strongly to 

 Professor Sedgwick's views. 



The discussion did not terminate with this letter, for in 

 the present number of our Journal we have to insert three 

 additional letters since published in the Literary Gazette. 



Were we not convinced that this discussion would form 

 an interesting episode in the history of English geology, we 

 might be blamed for occupying so many of our pages with 

 controversial matter. 



The following are the three additional letters : — 



1. Professor Sedgwick's Answer to Sir B. I. Murchison' s Letter 

 inserted in the Literary Gazette, and at page 355 of the Fifty - 

 second Volume of the Edinburgh Philosophical Journal. 



Cambridge, 5th April 1852. 



Aii absence from Cambridge during two weeks prevented me 

 from seeing your ' Literary Gazette ' of Mareh 20, at the time of 

 its appearance ; and it is through the kindness of a friend that I 





