208 . Association of Geologists and JS'aturalists. [Nov., 



liquid in which they are formed. He alluded to the calcareous 

 depositions on the shells of fresh water shell-fish — in the worms 

 of stills, lime is deposited, not at the top or bottom, but at a cer- 

 tain level, according to temperature — in steam-boilers, the lime 

 is deposited long before the water is a saturated solution. 



The remainder of the evening was spent by invitation at the 

 house of Dr. J. C. Warren. 



Morning SessiOxX — Fiiday, Sept. 24. 

 On the JVatchez Bluff Formation, by Dr. JV. D. Gale. 



Some time ago a fragment of a human ilium was found with 

 the fossil remains of the megatherium; it was therefore supposed 

 to belong to the same geological epoch as the latter. This was 

 undoubtedly a human ilium, and it was certainly found with the 

 remains of extinct animals. The object of the paper was to show 

 that the bone was deposited there at a comparatively recent period, 

 and was not coeval with the fossils among which it w^as found. 



The Natchez bluff is a fresh-water drift, from one hundred to 

 two hundred feet high — it consists of three beds; the lowest, a 

 bed of gravel, coarse at the bottom, and gradually becoming fine 

 sand; the middle is a bed of sand, of about eighty feet average 

 depth; the upper is a bed of loam — the whole resting on half- 

 solid tertiary clay. In the lowest bed the fossils are silicified; in 

 the same bed, they consist chiefly of oxygenous woods; in the 

 l.oam bed, (the most interesting,) land shells especially, and a few 



"•rine shells are found — it is in this loam bed that the bones of 

 tx.^ mastodon are found. 



This region abounds in grave-yards, made either by the abo- 

 rigines, or by the whites, who bury their dead on their own plan- 

 tations; this human bone was undoubtedly transported to the 

 ravine in which it was found, by a current, which swept it from 

 some of these burial grounds. 



Prof. Wm. B. Rogers made some remarks on the transporting 

 power of currents of water. Though much has been said and 

 written about this, very little is certainly known, as the data are 

 very insufficient; the subject is still open for investigation. Among 

 other causes of error, he mentioned that not only the velocity of 

 a current, but the nature of the bottom over which the stream 

 flows, should be taken into consideration; we want the rate of 

 velocity not only in the middle of the stream, but at the sides; at 

 different depths; and at the bottom. 



Prof. Agassiz remarked that the moving power, and rate of 

 water currents, was intimately connected with the transportation 

 of drift and boulders. It is indeed strange that the advocates of 

 the aqueous theory, having no definite data for discovering the 



