2 SURFACE GEOLOGY. 



arrive at the conclusions. This work was published in 1846, and directs geologists 

 to the only true method of arriving at the truth on this subject, viz: by a careful 

 investigation of the facts. 



The work, however, which first awakened a more especial interest in my mind, 

 probably because it came under my notice earlier than that of Mr. Darwin, was 

 Kobert Chambers' Ancient Sea Margins, published in 1847. Though dissenting 

 from some of Mr. Chambers' theoretical views, I saw at once that he had given us 

 an example of the true mode of getting at the truth on this subject. The nume- 

 rous cases of the elevation of terraces and beaches in Scotland above the ocean, 

 which this work contains, showed us that the same facts were needed in other 

 countries. I felt desirous of throwing in my mite towards the work, so far as the 

 valley of Connecticut River is concerned, though a bad state of health was a still 

 stronger motive for engaging in it. But so many new views did my labors open 

 upon me, that I have been stimulated to devote not a little time and labor to the 

 subject of surface geology during the last seven or eight years. And I have been 

 led to extend my observations beyond my expectations, not only in this country, 

 but in Europe. I find the field to be a very large one ; and that I have only 

 begun to explore it. I have seen enough, however, greatly to modify, and as it 

 seems to me to clarify, my views of the superficial deposits of the globe ; and I 

 venture to state my facts and conclusions before the scientific public. 



I use the term Surface Geology, to embrace the results of all those geological 

 agencies that have been in operation on the earth's surface since the tertiary 

 period. All the changes that have taken place since that time, I regard as belong- 

 ing to a single and uninterrupted formation, viz : the alluvial. The forces which 

 were acting at its commencement are still in operation: but they have varied 

 greatly in intensity at different times. Hence they have left various and peculiar 

 products, of which the following are most worthy of note. 

 Drift unmodified. 



Drift modified, which exhibits itself in the following forms :— 

 Beaches, ancient and modern. 

 Submarine Ridges. 

 Sea Bottoms. 

 Osars. 

 Dunes. 

 Terraces. 

 Deltas. 

 Moraines. 

 To which should be added the Erosions of the surface, from which the materials 

 have been derived. 



If we were to attempt to arrange these products in a chronological order, we 

 might designate four periods, beginning with the oldest. 

 The Drift Period. 



The period of Beaches, Osars, and Submarine Ridges. 

 The Terrace Period. 

 The Historic Period. 



