INTRODUCTORY REMARKS. 3 



All the agencies, however, that have produced the above phenomena, are still in 

 operation in some part of the globe ; therefore, the above periods are intended to 

 designate only the times when the different agencies were most intense, and pro- 

 duced their maximum effect. In a strict sense, they are contemporaneous. The 

 Historic Period, however, merely designates the time since man and contemporary 

 races have been upon the globe ; and though it marks out an important zoological 

 epoch, science has not yet been able to discover any correspondent geological 

 change ; though the presumption is, that one must have occurred, either local or 

 general. 



It is my purpose to go into a detailed description, in this paper, of only a part of the 

 phenomena of surface geology, as enumerated above. I started with the intention 

 of studying only the terraces and ancient sea-beaches in the vicinity of Connecticut 

 River. I found these subjects, however, so closely related to other points, that to 

 investigate a part would cast light upon the whole. The subject of erosions has 

 specially attracted my attention, and, since these are not confined to the alluvial 

 period, I shall treat of them in a separate paper. Unexpectedly, also, the marks 

 of what I suppose to have been ancient glaciers, descending from the Hoosac and 

 Green Mountains, fell under my notice ; and I have devoted another short paper 

 to an elucidation of the facts. In the present paper, I shall confine myself chiefly 

 to beaches and terraces, with their associated phenomena, submarine ridges and old 

 sea-bottoms. The subject of drift must, of course, receive some attention; since the 

 other forms of detritus are mainly modified drift. But I assume that the general 

 facts as to the phenomena of drift are understood by the reader. 



At the first, I did not expect to extend my observations beyond the valley of 

 Connecticut River. But, during the six years that have elapsed, I have travelled 

 extensively, both in this country and in Europe, with an eye always open to sur- 

 face geology, and usually with some kinds of instruments for measuring heights. 

 The facts thus obtained, sometimes indeed but few and unimportant, I shall em- 

 brace in this paper. 



It is well known that, usually, geological maps exhibit but little of surface 

 geology; save where the drift or alluvium is so thick that the subjacent rocks 

 cannot be ascertained. Were the surface geology well exhibited in such a region 

 as New England, these subjacent rocks would occupy but a small space. I have 

 appended to this paper, a few imperfect maps of this character. One represents, 

 as far as I have been able to trace it out, the surface geology of the Connecticut 

 valley; and others, certain spots, chiefly in that valley, much more limited. It 

 has been an object of strong desire with me, to construct a similar map of the whole 

 of Massachusetts ; and the Legislature of the State have given me assistance to col- 

 lect the facts. If life and ability to labor be continued to me long enough, I shall 

 hope to accomplish this object. The present paper is a preliminary to such a work. 



Several terms, mostly new, and necessary to a right understanding of surface 

 geology, will need definition. 



Drift is a mixture of abraded materials— such as boulders, gravel, sand, and 

 mud — mixed confusedly together for the most part, but sometimes laminated, and 

 occupying the lowest part of the unconsolidated strata, and lying immediately 



