PHYSICAL SCIENCE. 47 



of the problems to which we have just adverted. The older 

 theory which regards light as an emission of material particles, 

 was called upon to answer the enquiry, what becomes of 

 'matter thus absorbed ? while the undulatory theory, now 

 accepted as the great law of Light, has to explain what be- 

 comes of motion ? In the latter theory, closely linked as it 

 is with the doctrine of convertible forces, we undoubtedly find 

 the easier solution of the problem. But in this part of 

 science more especially, such questions are perpetually press- 

 ing upon us, each fresh fact (and the simplest are often the 

 most suggestive) giving access to objects of more advanced 

 thought and speculation. 



In passing thus cursorily over the sciences which deal with 

 the various forms of matter on our globe, and the forces 

 affecting them, we have said nothing of that Science now 

 become so vast in its objects and methods, which takes as its 

 province the outer structure of the globe itself; and the 

 changes, organic as well as merely material, succeeding one 

 another for ages on that surface which is now the dwelling- 

 place of man. Such seeming omission we may explain by 

 reference to previous Articles of this Review, in which the 

 present aspect of geological science, and the questions it 

 involves, have been considered at some length. In no one 

 department of Natural knowledge, we may safely affirm, 

 has greater zeal and activity been displayed, or with larger 

 and more successful results. We must repeat further that 

 Greology has (within the last thirty years more especially) 

 undergone a change which raises it far above the mere 

 history of the succession, location, or dislocation of strata, 

 and connects it inseparably with other branches of science 

 still more fruitful of discovery. Fossil Greology in particular, 

 the creation of our own time, affords a striking example of 

 what may be attained by zealous research, submitted to 



