Mineralogy and Geology. 269 
landslips caused. Colonel Wiley, a proprietor in this part of the state 
of Mississippi, and who well remembers the district before the year 
1812, assured me that the Mammoth ravine although now seven miles 
long, and in some parts sixty feet deep, with its numerous ramifications, 
has been entirely formed since that year when the earthquake occur- 
- He has himself ploughed some of the land exactly over the spot 
where the ravine is now situated. 
It is however enough for our purpose to affirm that whatever be the 
e years been con- 
siderably enlarged and lengthened, its banks presenting everywhere 
precipices in which the loam, unsolidified as it is, retains its verticality, 
as is the case with its counterpart, the loess of the Rhine. Land shells 
are seen in great numbers at the depth of about thirty feet from the 
top, and the fossil bones of the mastodon, and other extinct quadrupeds, 
are usually picked up in the bed of the stream, after they have been 
washed out of the undermined cliffs, where, however, some few have 
also been observed in situ. Under these circumstances, as I was given 
to understand, the human pelvis was procured at the base of the cliff. 
Even if it had been dug out in the presence of a practical geologist, 
it would have been necessary for him to re than usually on his 
guard against deception, for landslides have detached large masses 
from the cliffs, and these may easily cover human bones paddepert 
0 
country, may have been undermined. It is not rare to find on shoals 
and on the shores of the islands in the Mississippi at low water, numer- 
ous bones of man mingled with those of extinct animals washed out of 
the bluffs. In these cases the human bones are as black as the quadru- 
pedal fossils, having been apparently stained with peaty matter, in the 
soil where they were buried; but no geologist has ever ventured on 
this evidence, to infer the contemporaneousness of man and the fossil 
Specimens thus accidentally associated. 
Afier Lhad made up my mind that the remote antiquity of the hu- 
man bone at Natchez was questionable, and that its occurrence in the 
ravine might be explained in the manner above suggested, | found that 
Colonel Wailes, a friend of Dr. Dickerson’s, who accom nied us In 
part of our excursion, and who has also made a fine collection of the 
fossils of this neighborhood, not only shared my doubts, but had made 
the same conjecture respecting the probable manner in which the fossil 
may have been conveyed to the spot where it was found. I have the 
lour to be, Sir, yours, &c., Cuantes LyeE.. 
ll, Harley street, Dec. 7. 
ces of the Su ition of certain Minerals in some of the 
Metalliferous Deposits of Cornwall and Devon; by Wittiam Jory 
F 
and Catta Preta Gold Mines, (from the L., E. & D. Phil. Mag., Nov., 
1846, xxix, 359.)—The interesting communications of Messrs. Fox and 
Dana, induce me to present an abstract of observations on the superpo- 
