24 



SCIENCE. 



[N. S. Vol. XVIII. Xo. 444. 



Bascomb well near Mobile, to which we have 

 referred in our first note. At this well the 

 Grand Gulf, with its usual capping of Lafay- 

 ette, forms the surface. The boring reaches 

 the Pascagoula shell bed at about 700 feet, 

 and the bed containing Oak Grove fossils 

 (Chattahoocliee) at about 1,500 feet. From 

 the materials brought up we judge that about 

 180 feet at the top of this boring are in the 

 Grand Gulf; how much, if any, more of the 

 strata belongs to this formation we can not, 

 of course, say, but the main point to be noted 

 is that here the Grand Gulf lies far above the 

 Pascagoula, and the latter some seven or eight 

 hundred feet above the Oak Grove beds. 



5. The Coasts in Mohile and BaUwin 

 Counties, Alalmma, and in West Florida. — We 

 have already spoken in our first note of the 

 occurrence of the Grand Gulf down to within 

 a mile or two of the Gulf in Mobile County; 

 of its occurrence in Baldwin County on the 

 shores of Perdido Bay, where it makes a high 

 blufP. Recently we have seen the same forma- 

 tion making the greater part of a bluff, thirty 

 feet or more in height, on the very border of 

 Pensacola Bay in the city of that name. 



Now since a formation is bound to be 

 younger than the newest formation which it 

 overlies, and older than any which overlies it, 

 we are forced by the facts adduced above to 

 conclude that the Grand Gulf occupies a place 

 in the geological column somewhere between 

 the uppermost of the Tertiary formations as 

 yet determined by its fossils, viz., the 

 Pascagoula and the Lafayette. We will not 

 even say that the Grand Gulf represents all 

 the time and space between these two forma- 

 tions, for the borings near Mobile and the 

 bluffs on Perdido Bay at Pensacola, show 

 that if there are any post-Pascagoula Ter- 

 tiaries in Alabama and western Florida, the 

 Grand Gulf comes in between them and the 

 Lafayette. 



If any one should still maintain that the 

 Grand Gulf belongs anywhere in the Tertiary 

 column between the Buhrstone and the top 

 of the Pascagoula, we think the burden of 

 proof rests with him; he should show a single 

 section where Grand Gulf beds, of the char- 



acter described by Hilgard and accepted by 

 all the geologists of the gulf coastal plain, 

 may be seen intercalated between any two of 

 the Tertiary formations. 



If we seek to escape the legitimate con- 

 clusion from the facts above given of their 

 distribution and stratigraphical relations, by 

 assuming that the fresh-water Grand Gulf 

 beds of the west (Mississippi and Alabama) 

 find their marine equivalents further east in 

 the Chattahoochee series, we are confronted 

 with this fact, that- at the Chattahooche River, 

 and beyond through Georgia, the characteris- 

 tic fresh-water Grand Gulf beds, such as Hil- 

 gard has described them, overspread the coun- 

 try just as they do to the west, showing no 

 signs whatever of any transition into marine 

 deposits. It is needless to seek equivalents 

 when the thing itself is there. 



And, moreover, we now know for a certainty 

 that all across Alabama and in the type local- 

 ity of Dr. Hilgard, on Chickasawhay River in 

 Mississippi, both the fresh-water Grand Gulf 

 and the marine fossiliferous Tertiaries coexist 

 everywhere, the Grand Gulf above, the Ter- 

 tiaries below. 



The facts which we have presented above 

 may easily be verified by a few days' field work. 

 If they are susceptible of other construction 

 than that which we have placed upon them, or 

 if there are other facts incompatible with the 

 conclusions which we have reached, we stand 

 ready to modify or abandon our views, since 

 we are fully aware of our limitations, and of 

 the difficulty, almost the impossibility, of ar- 

 riving at the whole truth. If we have made 

 a small contribution towards it we ought to be 

 satisfied. 



No one can appreciate more than we do the 

 great work which Professor Dall has accom- 

 plished in our southern Tertiaries, and we 

 hope he may long continue active in the same 

 work, and bring us finally to a certain and 

 complete knowledge of the sequence of these 

 formations and of their contained fossils. If 

 we differ from him on some of the points pre- 

 sented above, it is because the facts seem to 

 compel us thereto. 



Moreover, we think he has hardly given due 



