Geology of the MusJcingum Valley. 21 



1. Commencing on the top of the hill, , above the grotto, which 

 is here two 'hundred feet in height, above low water in the Ohio, 

 there is a deposit of about forty feet, of an ash colored, clayey earth ; a 

 part of which has been formed from sedimentary precipitation, and part 

 from the decomposition of the argillaceous sandstone rock. — 40 feet. 



2. Friable, loose, slaty sandstone — easily decomposing — contain- 

 ing considerable mica, and a large share of argillaceous materials, 

 with some oxide of iron, giving it a light tinge of ochre, mixed with 

 the prevailing ash color. — 35 feet: 



3. Yellow, ochrey marl, with nodules of red oxide of iron scat- 

 tered through it. A few fresh water univalves, fossilized, and an 

 argillaceous cast of an extinct species of cray fish, the head much 

 more pointed than the recent species, have been found in this de- 

 posit. — 4 feet. 



4. Fine grained, compact sandstone, containing little mica, ex- 

 cept in the horizontal seams, v/hich divide the sandstone into lay- 

 ers of very uniform, but varying thickness, of from two inches to 

 twenty four inches. The upper and the bed face of the sandstone, 

 are very smooth, and require but little dressing to fit them for round- 

 ing into grindstones ; to which use this deposit is found to be well 

 adapted, and is very frequently apphed. It extends for many miles 

 along the face of the river hills, and quarries are opened in it at va- 

 rious places. Many hundreds of grindstones are annually sent from 

 this deposit to the towns on the river below. The thinnest layers 

 are on the top, and they grow gradually thicker as they descend. 

 No organic remains have been found in this rock, so far as I can 

 discover by repeated enquiries of the workmen, excepting a few 

 fragments of what appeared to be fossil wood. — 25 feet. 



5. Compact, or but partially stratified, tolerably coarse grained 

 sandstone, with fine silvery particles of mica imbedded ; cemented 

 by lime ; color, light ash, approaching, in some parts of the rock, to 

 white. Fracture very even, both in the line of its strata and in a 

 vertical direction, splitting easily into blocks of the best building 

 stone, of any dimensions, and, in the town of Marietta, it is exten- 

 sively used for architectural purposes. The upper portion of the 

 bed contains fragments of argillaceous stone, of irregular shape, 

 scattered through it. In this deposit is hollowed out the Grotto of 

 plants. — 50 feet. 



6. Red, or chocolate colored shale, or slaty marl. The upper 

 portion of the deposit, for six or eight inches, directly under the 

 sandstone, and on which the rock above reposes, is ash colored and 



