Association of American Geolofjisls ami Xuturalists. 149 



Fridays Proceedings. 



A paper by Dr N. D. Gale, upon the Natchez BlufF Formation, 

 was read by the secretary, Dr Wynian. Tliis Natchez Bkiff is 

 among the latest formations ; there is none other within fifty or 

 sixty miles of it later tlian this. It consists of beds of gravel, sand, 

 and loam. The gravel is composed of coarse pebbles near the base ; 

 the pebbles decrease as you approach the sand-bed. This is the 

 deepest ; in some places fi-om 60 to 100 feet thick. The fossils in 

 the gravel bed were desciibed. They are silicified, and belong to the 

 older secondary rocks, and are transported from distant geological 

 fields. Many of the specimens are worn to rounded pebbles, having 

 received this form by being transported by the currents. The fossils 

 of the other beds were also described. The Mastodon is found in, 

 not upon, the loam bed. 



Professor AY. B. Kogers remarked, in connection with the obser- 

 vations of the preceding paper, that the subject of the transporting 

 power of water in the force of rivers, currents, waves, &c., is one 

 which as yet stands in need of experimental investigation. We 

 have yet, indeed, no accurate data on the subject, and it would 

 form a most important contribution to geological science, were the 

 power of aqueous transportation really ascertained in numerical 

 fox-ce. No statements on this subject can be relied upon which do 

 not take into account as well the force and nature of the surface 

 upon which the matter is moved, as the velocity of the current and 

 the size and specific gravity of the transported materials. Professor 

 Rogers urged the investigation of the subject systcmaticaUy, as a 

 most important basis for much geological reasoning. 



Professor Agassiz said, that the rate of currents, as transporting 

 agents, was not accurately ascertained. There were no data to de- 

 termine the transporting power of the agent or currents which 

 transported the boulders and drift. But the data of the glacier 

 movements have been accurately determined. 



Mr Dana stated that publications had appeared in Ennland, 

 shewing the velocity of water ; but the deductions arrived at were 

 on mathematical and not experimental grounds. 



Professor Agassiz said, that in the early history of glaciers their 

 movements were explained on mathematical grounds ; but experi- 

 ment had shewn that the whole matter was erroneous. 



Professor W. B. Rogers gave an abstract of a series of researches 

 lately made by himself and" Professor R. D. Rogers, on the absorp- 

 tion of carbonic acid by liquids. Their researches, besides applying 

 to most of the liquids included in the well-known experiments of 

 Saussure, embrace many others. The njethod of research involving 

 a peculiar apparatus for securing permanency of temperature and 

 moisture, is entirely new, and i.s regarded as capable of very great 

 accuracy, while it has the further advantage of being applicable to 



