July 3, 1903.] 



SCIENCE. 



25 



weight to the evidence which we brought for- 

 ward in our first note, and certainly he does 

 not correctly represent our position in some 

 of his comments on that note, as, for in- 

 stance : 



1. He thinks that our assumption of the late, 

 possibly Pliocene, age of the Grand Gulf beds, 

 if it should prove correct, is merely an equiv- 

 alent of the idea of Dr. Hilgard cited by him, 

 and, therefore, not new. 



Dr. Hilgard's idea was that these beds repre- 

 sent all the time and space between the Vicks- 

 burg and the Lafayette; ours is that they rep- 

 resent a very small part only of that time and 

 space, viz., the part between the Lafayette 

 and the uppermost of the known Tertiaries of 

 the Gulf coast — the Paseagoula, and very 

 probably not even all of that. If a part is 

 equal to the whole, then the equivalence is 

 established, and we stand convicted. 



2. " The beds which Messrs. Smith and 

 Aldrich call ' Grand Gulf ' in their communi- 

 cation to Science are not the same" (i. e.. 

 Professor Ball's ' typical Grand Gulf ') " but 

 are the non-fossiliferous upper portion at the 

 other end of Hilgard's Grand Gulf section." 



The clays containing lignite and fossil palm 

 leaves, described by Hilgard at Powe's on 

 Chickasawhay River in Mississippi, have been 

 fixed upon by Professor Dall as his ' typical 

 Grand Gulf ' beds, and have been classed by 

 him as Oligocene (Science, December 12, 

 1902, p. 946). Now from this tj-pe locality 

 Dr. Hilgard traveled southward down Chick- 

 asawhay and Paseagoula, giving details of 

 exposures of the Grand Gulf as far as Dwyer's 

 ferry, ten or twelve miles from the gulf. Al- 

 though he then saw no contact of the Grand 

 Gulf with any underlying formation, owing, 

 no doubt, to the stage of the water, yet this 

 formation may be seen, as above described, 

 resting on the Paseagoula shell marl on the 

 Chickasawhay, a few miles above its confluence 

 with Leaf River. And furthermore, the 

 Grand Gulf at this point consists of clays, 

 sands and lignitic clays, with silicified trunks 

 of trees. The same formation is at the sur- 

 face thence back to the type locality near 

 which it is seen resting upon Vicksburg lime- 

 stone. Here then the unquestioned Grand 



Gulf, with Hilgard's hall-mark of genuineness 

 upon it, rests upon the beds of Upper Miocene 

 (or Pliocene) age, called the Paseagoula, just 

 as they rest upon the Eocene Vicksburg lime- 

 stone twenty miles further north. Both Hil- 

 gard and Johnson have given details of nu- 

 merous other fossiliferous Grand Gulf beds in 

 these parts of Mississippi. These are the beds 

 which we have called Grand Gulf. And fur- 

 thermore, we find lignites and lignitic clnys 

 with leaf impressions in the formation nvcr- 

 lying the Miocene at Coal Bluff and Roberts 

 in Escambia County, Alabama ; we find the 

 lignitic matters in the same beds down to the 

 water's edge on Mobile Bay, so that certainly 

 all the beds which we have been calling Grand 

 Gulf are fossiliferous precisely as are those 

 described by Hilgard which Professor Dall 

 accepts as his typical Grand Gulf. Nor have 

 we been writing about the upper part of the 

 formation only, as the bluffs on Conecuh River 

 demonstrate. If the Grand Gulf beds which 

 there rest on the Vicksburg limestone be 

 counted as the lower beds, then the beds of the 

 same formation resting on Miocene fossilifer- 

 ous sands, four miles further south, can not 

 be very much higher up, especially in view of 

 the fact that the Grand Gulf beds are every- 

 where very nearly horizontal. And even ujion 

 the assumption of a steeper dip, since the 

 Grand Gulf covers the country down to the 

 gulf, a distance of thirty or forty miles from 

 the Conecuh River localities, those beds which 

 form the surface over only four miles (or one 

 tenth of this area) certainly would not be- 

 long to the Tipper portion. 



3. " By means of paleontological data, * * * 

 I have been enabled to fix the age of differ' nt 

 l>orliuns of the original heterogeneous series 

 as uppermost Oligocene (transitional) and 

 Chesapeake Miocene, which is fully confirmed 

 by the facts now cited by your correspond- 

 ents." 



Langdon's discovery along the Chatta- 

 hoochee in 1S87 first showed beyond all ques- 

 tion that fossiliferous marine beds occupied 

 a part of the geological column which Hil- 

 gard once thought to be covered by his Grand 

 Gulf beds alone. Langdon gave the name 

 Chattahoochee to these deposits, which he 



