87 



in summer. The country around Bigbone Lick, and for a consider- 

 able distance on both banks of the Ohio, above and below it, is 

 composed of blue argillaceous limestone and marl^ constituting one of 

 the oldest members of the transition or Silurian system. The strata 

 are nearly horizontal and form flat table-lands intersected by nume- 

 rous valleys in v^'hich alluvial gravel and silt occur ; but there is no 

 covering of drift in this region. The drift is abundant in the north- 

 ern parts of Ohio and Indiana, but disappears almost entirely before 

 we reach the Ohio. 



Until lately herds of buffaloes were in the habit of frequenting 

 the springs, and the paths made by them are still to be seen. Num- 

 bers of these animals have been mired in the bogs, and horses and 

 cows have perished in like manner. Along with their remains are 

 found innumerable bones of Mastodon, Elephant, and other extinct 

 quadrupeds, which must have visited these springs when the valley 

 was in its present geographical condition in almost every particular, 

 and which must have been mired in them as existing quadrupeds are 

 at present. The mastodon remains are most numerous and belong 

 to individuals of all ages. The mud is very deep, black, and soft. 

 In places it is seen to rest upon the limestone, and at some points 

 it swells up to the height of several feet above the general level 

 of the plain and of the river. It is occasionally covered by a 

 deposit of yellow clay or loam, resembling the silt of the Ohio, 

 which is from 10 to 20 feet thick, rising to that height above the 

 creek and often terminating abruptly at its edges. This loam has 

 all the appearance of having been deposited tranquilly on the sur- 

 face of the morass and of having afterwards suffered denudation. 

 The Mastodon and other quadrupeds have been mired before the de- 

 position of the incumbent silt, for a considerable number of fossil 

 bones have been found by digging through it. Accompanying the 

 bones are freshwater and land shells, most of which have been iden- 

 tified by Mr. Anthony with species now existing in the same region. 



Mr. Lyell observes that the surface of the bog is extremely uneven, 

 and accounts for it partly by the unequal distribution of the incum- 

 bent alluvium which presses with a heavy weight on certain parts of 

 the morass, from which other portions of the surface are entirely free. 

 He also attributes it in part to the swelling of the bog where it is 

 fully saturated with water near the springs. 



The author is of opinion that the fossil remains of Bigbone Lick 

 are much more modern than the deposition of the drift, which 

 is not present in this district. But although the date of the im- 

 bedding of these mammalian fossil remains is so extremely mo- 

 dern, considered geologically, it is impossible to say how many 

 thousand years may not have elapsed since the Mastodon and other 

 lost species became extinct. They have been found at the depth of 

 several feet from the surface, but we have no data for estimating the 

 rate at which the boggy ground has increased in height, nor do we 

 know how often during floods its upper portion has been swept away. 



Ohio. — The Ohio river immediately above and below Cincinnati 

 is bounded on its right bank by two terraces consisting of sand, gra- 



