218 Geological Society, 



cies, with a view to discover the relative ages of distant and uncon- 

 nected tertiary deposits. 



Of the Work so honoured by the Royal Society, the third edition 

 has been lately published : in this edition some opinions formerly 

 expressed have been modified or renounced, and much new matter 

 lias been introduced ; the phaenomena of springs and Artesian wells 

 have been more fully treated ; the theory of elevation has been en- 

 tered into more at large, the author still controverting that theory. 

 A chapter, almost entirely new, points out the probable causes of 

 volcanic heat ; objections are advanced against the doctrine of the 

 central fluidity of the earth, and especially the intense heat attri- 

 buted by some writers to the internal nucleus. Mr. Lyell considers 

 how far chemical processes in the interior of the earth may generate 

 volcanic heat, and what may be the effect exerted by currents of 

 electricity. Sir Humphry Davy's theory of an unoxidated metal- 

 lic nucleus is considered, and it is suggested that compounds re- 

 sulting from the action of water upon metallic bases may be again 

 deoxidated by the hydrogen set free in that process. The author 

 has also given a more complete view of his opinions respecting the 

 origin of caverns, and the manner in which they have been filled 

 with breccia and the bones of animals. In illustrating this sub- 

 ject, he refers particularly to the recent discoveries of MM. Virlet 

 and Boblaye in the Morea. His sketch of the principal secondary 

 formations is also considerably enlarged. 



Two other publications have issued from the press during the 

 last year, which are eminently deserving of your attention. The 

 first of these, entitled " A Treatise on Primary Geology," originated 

 in great measure from a discussion that took place at a Meeting of 

 the Geological Section of the British Association at Cambridge, and 

 was drawn up with a view to the further consideration of the chief 

 questions which it embraces, at the subsequent Meeting of the same 

 body at Edinburgh. 



Dr. Boase begins by describing the composition and relation of 

 the several Primary Rocks, combining the accounts of geologists in 

 various parts of the world with the results of his own laborious in- 

 vestigations in Cornwall. I regret, that within the limits to which I 

 am restricted, it is impossible for me to do justice to the merits of 

 this important work ; I must confine my observations to a few of its 

 most characteristic features. Dr. Boase is of opinion that the con- 

 nexion between Unstratified and Stratified Rocks shows that they had 

 a common and contemporaneous origin. He observes that granitic 

 masses are as complex in their composition as stratified rocks, and 

 form sometimes distinct regular beds, highly inclined and alternating 

 with one another; that the elvans, or insulated beds of granitic rock, 

 always partake of the nature of the containing slate, and have the 

 same basis ; that the difference between the granite and killas, or 

 elvan, in Cornwall is often feebly marked, and still more feebly the 

 difference between the granite and gneiss of Scotland and Germany; 

 as little difference is there between the granite of the Alps and the 

 talc slate adjoining. Where the granite changes its character, a cor- 



