SURFACE GEOLOGY. 44a 
coal and of the sandrock of the Coal Measures, all evidently of home 
origin. The pebbles of coal could not have traveled far—the material 
is too soft to endure the friction and rough usage of a long journey. 
The Drift terraces are found along the Ohio, Muskingum, Licking, 
Hocking, and Scioto rivers, but on no others in the Second District. 
These are the only streams whose sources lie within the area of the general 
Drift, and, consequently, the only ones which could obtain the materials 
needed for true Drift terraces. These terraces have been more or less 
wasted and reduced in height since they were formed, but eighty feet 
above the stream is about the elevation of those best preserved. Being 
dry and easily drained, they afford desirable locations for the towns and 
villages of the present inhabitants, as they did for the Mound-builders, 
whose finest works are generally upon them. Zanesville, Marietta, Lan- 
caster, Gallipolis, Ironton, Portsmouth, and other towns of less size, are 
built wholly or in part on Drift terraces. The Ironton terrace has more 
clay mixed with the sand than is usual. The terrace on which a part of 
the city of Lancaster is built, the new and beautiful court-house having 
a commanding site on the summit, is one of the old Drift gravel banks. 
It is from seventy-five to eighty feet above the present bed of the Hocking 
River. We have now only a remnant of the original terrace, for the 
waters have swept around in rear of it, and left only an insular hill in 
the broad fertile valley. On the southern edge of the present hill the 
gravel is very coarse. This gravel at some points is found to be cemented 
together by carbonate of lime, and a stratum of coarse pudding-stone has 
been formed, which is used for rock-work, ferneries, ice-houses, etc., 
where picturesque effects are desired. A similar pudding-stone is found 
in a Drift terrace a few miles below Logan. 
Marietta is built on a large and beautiful terrace, formed at the conflu- 
ence of the Muskingum and Ohio rivers. It is composed of sand and 
gravel, the sand in some places fine enough for molders’ use. The gravel 
is often quite coarse, and contains pebbles of considerable size. In the 
‘south-eastern portion of the terrace, where it is crossed by Putnam street, 
there is a well-defined horizontal layer of fine blue clay, which indicates 
that at one time the currents of the two streams were of such equal level 
and equal force as to form an eddy of still water, from which the fine 
clay sediment was deposited. | 
The terraces at Columbus and vicinity are broader than the usual val- 
ley terraces, and constitute a part of a far wider outspread of Drift mate- 
rials in the more flat country to the north The transition from the val- 
ley Drift to the general northern Drift, as it has been distributed and 
arranged by water, is almost imperceptible. Perhaps the same aqueous 
