Mabch 13, 1897.] 



SCIENCE. 



411 



4tendre les parties extremes du spectre au 

 dela des limites observees par Fraunhofer. 

 Les nouvelles parties du spectre, avec leur 

 raies sont representees dans la Fig. 4, qui 

 est la reproduction du dessin communique 

 par Mr. Mathiessen. 



PROFESSOR FONTAINE AND DR. NEWBERRY 

 ON TEE AGE OF THE POTOMAC FORMATION. 



The appearance at this time of two im- 

 portant works on the Potomac formation, 

 though both of them have been long de- 

 layed in publication, is peculiarly oppor- 

 tune in view of the discussion now going on 

 in relation to the age of that formation. 

 These works are first, that by Professor 

 Fontaine on the Potomac Formation in 

 Virginia,* and second, that of Dr. J. 8. 

 !N'ewberry, on The Flora of the Amboy 

 Clays. t 



The greater part of the matter of the 

 first of these works was originally sub- 

 mitted by Professor Fontaine as an intro- 

 duction to his important work on The Flora 

 of the Potomac Formation, J giving a some- 

 what detailed account of the stratigraphical 

 relations of the Potomac formation in 

 Virginia. But it was thought best to 

 omit this introductory part and publish 

 it separately. Owing to causes which 

 need not be here enumerated, the publi- 

 cation of this part of his work was long ne- 

 glected, but is now hapily before the scien- 

 tific world. 



As its name implies, this treatise is con- 

 fined mainly to those portions of the Poto- 

 mac formation which lie south of the Poto- 



* The Potomac Formation in Virginia, by William 

 Morris Fontaine, Bull. U. S. Geol. Surv., No. 145, 

 "Washington, 1896. 



t The flora of the Amhoy Clays, hy John Strong 

 Newberry. A posthumous work, edited hy Arthur 

 HoUiok. Monographs of the U. S. Geological Survey, 

 Vol. XXVI., Washington, 1896 (erroneously dated 

 1895). 



X The Potomac or Younger Mesozoic Flora, 2 Vols, 

 text and plates. Monographs of the U. S. Geo- 

 logical Survey, Vol. XV., Washinston, 1889. 



mac River, i. e., almost exclusively to the 

 State of Virginia, and only contains inci- 

 dental references to the condition of things 

 in Mai-yland. A consequence of this is that 

 it deals wholly with the Older Potomac and 

 does not attempt to discuss the prolonga- 

 tion of the formation through New Jersey 

 and northeastward, where all the beds thus 

 far found belong to the Newer Potomac, 

 which finds its greatest exemplification in 

 the Raritan and Amboy Clays. 



The second of these works, on the con- 

 trary, deals exclusively with the Newer Po- 

 tomac, but under the term Amboy Clays 

 Dr. Newberry expressly included all that 

 was known to him of those beds which oc- 

 cupy the north shore of Long Island and 

 are found all the way from Staten Island to 

 Marthas Vineyard. Although I have desig- 

 nated these latter beds as the Island Series, 

 and have sufiiciently demonstrated the just- 

 ness of this subdivision, I have at the same 

 time admitted that the character of the flora 

 is substantially the same throughout. 



We thus have two new contributions to 

 the subject under discussion written by able 

 men who are not exclusively nor chiefly 

 paleobotanists, but are known to the world 

 as geologists of the first grade, each of whom 

 prior to writing his work had devoted many 

 years to an exhaustive study of the forma- 

 tion to be dealt with. Although much has 

 been learned since the date at which these 

 works were written, it is not proposed in 

 this paper to make special reference to such 

 discoveries, as they have been for the most 

 part fully set forth in a series of papers by 

 Mr. David White, Dr. Arthur Hollick and 

 myself, an acquaintance with which will be 

 assumed on the part of the reader.* But 



*See Bull. Geol. Soo. Am., Vol. I., p. 554 ; Vol. 

 VII., p. 12 ; Am. Journ. Sci., SdSer., Vol. XXXIX., 

 p. 93 ; Trans. N. Y. Acad. Sci., Vol. XI., p. 96 ; Vol. 

 XII., p. 1, 222 ; Vol. XIII., p. 122 ; Bull. Torr. Bot. 

 Club, Vol. XXI., p. 49; Fifteenth Ann. Rept. U. S. 

 Geol. Surv., p. 307 ; Sixteenth Ann. Kept. U. S. Geol. 

 Surv., p. 463. 



