XYIII PEEFAOE. 



In allotting these tasks to Messrs. Foerste and Woodworth, I turned 

 over to them the small share of the results that I had obtained in woi'k 

 on this field which seemed likely to be in any way helpful to them. 

 Those contributions were, however, so limited in quantity, at least as regards 

 the difficult matters of detailed structure, that the sections of this mono- 

 graph which appear under their names are essentially their own. 



A considerable range of facts, especially those which relate to the inti- 

 mate structure and the metamorphism of the rocks, have not been to any 

 extent treated in the following pages. This omission has been designedly 

 made for the reason that the inquiries necessary to a consideration of these 

 subjects would have required the services of a trained petrographer for 

 a long time. In a like manner, the very interesting and important vegeta- 

 ble remains which abound in certain parts of the Coal Measures have been 

 passed by, though they well deserved an extensive study. Thus it has 

 come about that the extremely varied rocks which border the Paleozoic 

 stratified series, or which are in the form of islands in its areas, are not dis- 

 criminated according to their lithological varieties, but are indicated merely 

 as pre-Carboniferous, and the paleontology of the basin, which includes 

 extremely interesting groups of fossil insects and other organic remains, is 

 in no wise presented. These and other omissions deprive this monograph 

 of all claims to being a full account of the geological phenomena of 'the 

 basin; it should, indeed, be considered as a contribution only to the strati- 

 graphical and dynamic history of the area. 



"Where the statements of my collaborators are not questioned by me in 

 footnotes, it should be understood that I approve of them as, so far as I 

 can see, the best that can be made concerning the facts with which they 

 deal. In only one instance has conference failed to bring about a concur- 

 rence of opinion concerning any question of moment This is in relation 

 to the value of the division which Dr. Foerste has termed the Kingstown 

 series, which he regards as distinct from the Aquidneck, which overlies 

 it. To my mind it appears to be only a local thickening of the last- 

 named series, with a similarly local addition of sandstones. The dis- 

 agreement is not only in relation to the propriety of separating these two 

 sets of rocks, but also as to the thickness of the lower series. It seems 

 to me most likely that the apparent increase in the depth may be reasonably 

 explained by the occurrence of rather compressed folds, the axes of which 



