THE ATLANTIC OCEAN. 191 



earth, ocean, and atmosphere all come within its sphere, as 

 well as those great and mysterious forces gravitation, heat, 

 light, and electricity by which these several portions of 

 our planet are so powerfully and incessantly acted upon, it 

 will be seen how closely the subject is linked with every other 

 research into the world of nature around us. Our country- 

 woman, Mrs. Somerville, has well expounded these relations 

 in her admirable volumes on Physical Geography. The 

 Physical Atlas of Berghaus, a valuable German work, pre- 

 ceded the publication in this country of the more extensive 

 and elaborate ' Physical Atlas of Natural Phenomena ' by 

 Mr. A. Keith Johnston, of which it would be difficult to 

 speak in terms above the mark of its actual merits. Em- 

 bracing every part of the subject, it delineates to the eye 

 as well as the mind and far better than by any verbal 

 description those complex relations of physical phenomena 

 on the globe, which are the true foundation of Physical 

 Geography. 



Of all branches of science, no one contributes so largely to 

 our knowledge of the actual condition of the globe as Geo- 

 logy. By drawing its conclusions from a long series of ages, 

 this science has given us the means, in no other way equally 

 attainable, of studying and explaining the present aspects of 

 the earth we inhabit. Such are, the power obtained through 

 the study of fossil remains, of identifying strata in localities 

 the most remote, and thus fixing the common epoch (how- 

 ever long its duration) of certain states or changes of the 

 crust of the globe ; the facts discovered, which prove the 

 gradual upheaval of portions of the earth's surface and the 

 slow depression of others ; the proofs from the inclination 

 and contortions of strata, from the alterations of the older 

 strata, and from the position and elevation of the unstra- 

 tified rocks, that other changes, more abrupt and violent, 

 have occurred from subterranean forces of expansion or 



