38 The Lower Cretaceous Deposits of Maryland 



But the discovery in them at Baltimore, by Professor Tyson, of stumps 

 of eyeads would seem to bring them into near relation with the formation 

 at Fredericksburg containing similar remains, and to favor their being 

 referred, at least in part, to the horizon of the upper Jurassic rocks. 

 Possibly we may find here a passage group analogous to the Wealden of 

 British geology. Whatever may be the result of further discovery, it 

 would seem to be premature at this time to assume the whole of these 

 deposits from the Potomac northward as belonging to the Cretaceous 

 series. 



" Where the Tertiary or Cretaceous rocks are present in this belt there 

 is, of course, no danger of confounding the superficial gravel and cobble- 

 stone deposit with the formation just described, but in their absence, 

 which is usual in the river valleys, this deposit rests immediately on 

 the broken and denuded surface of the Secondary, and by the inter- 

 mixture of materials makes it more difficult to discriminate between 

 them. 



'^ Excellent opportunities for observing the contact of the superficial 

 deposit with the denuded and much older formation below are presented 

 in the neighborhood of Washington, among which may be specially men- 

 tioned the vertical cut at the extremity of Sixteenth street, at the base 

 of the hill occupied by Columbian College, and also the continuation of 

 Fourteenth street, ascending the same hill. At the former locality the 

 crumbling felspathic sandstone, or slightly adhering sand, is exposed to 

 a height of about 35 feet, with a very gentle eastern dip, and having the 

 color, composition, and diagonal bedding characteristic of the Fredericks- 

 burg and Aquia Creek sandstone. The gravel and cobblestone deposit 

 lying upon it descends with the slope of the hill to the general plain 

 below, resting at a somewhat steep angle against the denuded edges of 

 the underlying beds. From this and other localities it becomes obvious 

 that the latter formation has been deeply and extensively denuded before 

 and during the deposition of the surface strata, which form the chief 

 subject of this communication." 



Professor Fontaine commenced his work on the Potomac at about this 

 time, publishing during 1879 a series of three articles in the American 



