106 CEMENT MATERIALS AND INDUSTRY. I hill. 24 
from the same bed examined at other localities in this area. Thp 
fresh rock is grayish white and sandy. 
The shell bed at the base of the formation is exposed at the edge c 
the highland near the Columbus-Albrook road, 1 mile northwest c 
Columbus. The same bed is exposed also at the crest of the highlan 
1 mile north of the town. The chalk marl highest in the formatio 
occurs in the cultivated fields between the outcrop of the shell be 
and the town. 
From the vicinity of Columbus eastward to the end of the forma 
tion in the Washington area the whole of the Saratoga formatio 
outcrops or is covered only lightly by soil. Throughout this exterj 
the basal shell-bed member of the chalk marl is almost continuous! 
exposed, except in the immediate bases of the valleys, and may b 
easily located through the open fields by means of the abundant shell 
weathering upon the surface. 
Between Columbus and the railroad north of Washington the chalk 
marl was not found to outcrop more than 30 feet in thickness, an 
usually 10 to 20 feet of the lower part was all that was exposed. 
The overlying greensand marl is more friable than the Saratog 
chalk marls, and its soil descends and conceals the contact betwee 
the two as well as the upper part of the latter. A section of th 
Saratoga marl with better exposures than are usually found occur 
along the railroad north of Washington. 
The north cut on the railroad is in a blue clay-marl 30 to 50 fee* 
below the base of the Saratoga formation. It is 10 feet deep am 
about 300 feet long. The marl in this cut, which was originally blue 
is weathered a creamy yellow to a depth of about 8 feet. It is tran 
sected by many joints, which pass nearly vertically across the beddiiij 
and continue down below the base of the cut. Along these joints 
even below the zone of general weathering, the blue color of the mai 
is changed to yellow for a distance of several inches. 
Analysis 15, page 111, is of the unchanged blue marl from the bal 
of the cut, 10 feet below the soil. The fresh marl is friable when dr 
and plastic when wet. It has a very line texture and contains scarce! 
perceptible grit, yet the analysis shows it to contain 4-3 per cent 
silica and 6.5 per cent of clay. Nearly 40 per cent of this silica is 
the form of impalpable sand. 
The shell bed, the base of the Saratoga formation, is exposed in t 
field southwest of this railroad cut. The middle cut is one-third of 
mile south of the north cut and is in the lower part of the Sarato 
chalk above the oyster-shell bed. This cut is 300 feet long and b 
a few feet deep, exposing an estimated thickness of 15 feet of rock 
The structure of the rock indicates a low inclination toward the south 
but is not sufficiently clear to determine the degree of dip. Ditchei 
above the south end of the cut expose about 25 feet of chalk mar 
