on the east side of the Scioto opposite the extreme upper end of the Camp commonly show 70 to 100 feet of sand at this horizon. These last are not typical, however, because they are located on the kame moraine and the material they penetrate is not identical in origin with the terrace gravels, though the records appear the same.

GROUND WATER

The gravels and sands which fill the Scioto Valley generally carry water up to about the level of the river, and in the terraces well back toward the rock hills the water stands well above the river level. Although the terraces may be readily distinguished topographically, their sands and gravels abut against, and very possibly are interfingered with, those of the kame moraines on the east side of the river in the northern part of the quadrangle. Similarly they abut against the old Illinoian gravels southeast of Chillicothe, though not interfingered with them. The water body which permeates the gravels of the river valley is not bounded by the lateral limits of the terraces, but is continuous with and indistinguishable from the waters which permeate these neighboring gravel masses.

The amount of water available at any place and depth in the valley filling depends largely on whether the material is sand or gravel. Where the material is chiefly sand, it may be impossible to complete a well in the presence of ample water because of the constant movement of sand into the bottom of the pipe. In all wells in which thick loose sand beds have been found they have been penetrated until a gravel bed is encountered which not only usually carries a splendid volume of water but permits the satisfactory completion of the well. In exceptional cases, failure to find such gravel bed has caused the abandonment of the well. Though the sands may be filled with water, when such a gravel bed is encountered, the water in the gravel almost invariably flows with so much greater ease into the well, that it shows a strong head, rises in the pipe half the depth of the well, more or less, and is regarded as a distinct vein.

Wells near the Scioto River, and extending only to the water table or but slightly below it, will undoubtedly be influenced by the river. If the river has been low for a considerable period, and the ground water level has fallen to near the river level, a sharp rise of the river would pour a considerable amount of water from the river into the surrounding gravels, unless there should be locally sufficient rain at the same time to raise the water table in the gravels at an equal rate, an occurrence that would be unlikely due to the time that the absorbed rain water requires to percolate into the gravels to river level. Since the water body in the gravels is fed chiefly from direct rainfall, from run-off from neighboring hills and small streams, which might require several hours of concentration to effectively raise the ground water level, it appears that this relationship may be brought into being frequently.

A

B

C

D

Fig. 14.-Diagrams to show the zone of ground water partially supplied from the Scioto River under the influence of flood conditions. A. After prolonged low-water, normal ground water moving toward river. B, C. Sharp rise in river, with a much slower rise in the ground water flowing toward the river on either side. This results in flow of water from river into bordering gravels. If the rise is unaccompanied by local rains, there will be no rise in the normal ground water level on either side, except as water flows in from the river. D. River fallen to low-water again, ground water level falling more slowly and ground water moving toward river. Obviously the zone of river influence on ground water is not fixed, but varies with conditions accompanying the rise.

It is not possible to say what is the extent of this zone of river influence, either vertically or horizontally, but the former is probably not much more than the vertical range of the river, 25 feet, and the latter is probably not more than a few rods. Except for this zone, the mass of water in the porous filling of the Scioto Valley is not to be regarded as Scioto River water. It is the result of absorption into the valley filling of a large percentage of the rain falling thereon, or water running onto it from the surrounding rock hills, and, excepting the prism of river influence just described, it is maintained from such sources, not from the river.

The water for Camp Sherman and for Chillicothe is obtained in the gravel filling of the valley, the former at a depth of about 55 to 85 feet below river level, the latter from wells in Yoctangee Park near the Scioto but at depths of about 70 to 80 feet below river level.

GRAVEL

The terraces of the Scioto River afford an inexhaustible supply of gravel. For road dressing it is excellent in quality, but for concrete it cannot be regarded as first-class in its natural state. It's a sandy

A.-Terrace of Wisconsin gravel and sand, freshly dissected along margin by steep-walled gullies. In the distance, the much older, higher terrace of Illinoian gravel. River Bridge, east of Chillicothe.

SCIOTO VALLEY TERRACES

limestone gravel, with a moderate percentage of granitoid pebbles and a small percentage of sandstone pebbles. The granitoid pebbles are occasionally soft from decay, and there are numerous fragments of shale. The last are the chief objection. They are from the Ohio shale and frequently when they are unweathered and sound and solid, may escape detection but they are none the less elements of weakness in concrete. Many localities would yield a gravel satisfactory for temporary constructions or for structures in which no unusual strength demands are made on the concrete. These gravels can be greatly improved by vigorous washing, which not only removes the dust but the decayed granitoid and shale pebbles, and probably many shale fragments that would appear sound. It is probable that there are places that are exceptional to this general description, where washing would not be necessary. The only one which has been seen is at Peppers on the south line. of the quadrangle; the gravel there seems to be unusually free of shale, but the face was inadequately exposed and the examination not thorough.

The general character of the gravel is shown in the pit of the Chillicothe Sand & Gravel Co., at the lower end of the Camp. Three random samples totalling 478 pebbles from inch to 2 inches in diameter, showed 4.6 per cent of sandstone or crumbly granitoid pebbles and 6.9 per cent of shale pebbles, by number. In size the shale pebbles run considerably smaller than the average and the percentage by volume would be proportionally less. These gravels, when washed, yield a product that is reported as first-class and was used as such in constructions by the U. S. Government; the product is accepted by the State Highway Commission of Ohio as grade A gravel, and used as the basis of the wearing course in concrete roadways, a very exacting use for concrete.

Small pits along the Columbus Pike north of Andersonville show a much higher percentage of shale than the sample described above. The gravel in the large pit of the B. & O. Railroad 5 miles southeast of Chillicothe also shows many shale fragments, which are in part derived from large crumbling blocks in a layer half way up the pit, that cannot be eliminated in quantity production. Concrete in bridge abutments made from these gravels is behaving apparently satisfactorily except as numerous small deep pits are forming on the surface where these shale fragments are weathering out; the pebbles are proportionally as numerous in the body of the concrete as at the surface.

Considerable gravel for local use is obtained in the river bottom at the Main Street bridge, Chillicothe. It is clearly a river gravel, with mussel shells and lumps of earth, which would prove about equally objectionable in a concrete devised for strength or abrasion.

Washing may be accomplished by the river as well as by artificial methods. Just above the Bridge Street bridge at Chillicothe on the Scioto River is one of the most extensive gravel bars within the Camp