Vlll 
THE QEOLO&IST. 
cause could have been adequate to the formation of all the va- 
rieties of superficial detritus/^ 
It is not our purpose to say all that has been done in each of 
these divisions — the "opinion^'' is all that we can grapple with in 
the allotted space, and we can only put it upon record that each 
of these several questions bears reciprocal relationships to the 
others, as portions of the grand theory. 
Amongst the essays we have published in the present volume 
we would refer to 
1. Prof. HitchcocFs on the Phenomena of Drift in the Uni- 
States, p. 34. 
2. Mr. Couthoy on Icebergs, p. 35. 
3. Prof. H. D. Rogers on Striated Surfaces in Pensylvania, 
&c. p. 40. 
4. M. Daubree on the Erratic Phenomena and Diluvium of 
Sweden and Norway, p, 41. 
5. Mr. Binney on the Lancashire and Cheshire Drift, p. 112. 
6. Mr. Harkness on the Glacial Theory, p. 122. 
7. Mr. Lyell on the elevated Beaches and Boulder Formations 
of the Canadian Lakes, p. 130. 
On the Formation of Coal. — The extension of observation on 
this subject, both in the European and American continents, has 
led to the establishment of the diverse views of various geologists 
on this important question. Mr. Logan in Pensylvania, and sub- 
sequently in Wales, has turned his attention to the accompanying 
phenomena observable in both countries, and connected with 
both purely carbonaceous and anthracitic coal. ]\Ir. Rogers in 
other parts of the United States has been engaged in similar in- 
vestigations ; and Mr. Binney in our own country, has turned 
his attention to the same question ; and for which he has such 
ample opportunities in his proximity to our Lancashire Coal-fields. 
* Mr» Murchison's Geological Addi*ess, 1843, p. 92. 
