82 The American Geologist. February. 1904. 
household of nature they are of greatest importance in so far as 
moit, if not all, of the water-courses of the region head in this 
deposit. The rain-water as well as the melting snow and ice, 
leceived either directly or indirectly, seeping through the till 
down to this level, supplies not only the creeks, brooks and 
biooklets by terminal and lateral leakage, but also a great num- 
bfr of ponds, the waters of which are found to be relatively 
pure, which would not be the case, if they did not receive their 
si-ij'ply, to sonie extent at least, from below. 
b : The Blue and Ydlozv Till. 
Overlying the sands and gravels of the drift, the till 'con- 
stitutes far the greater amount of the surficial topography of 
the region, excepting only those portions which are occupied 
by the loess. We usually distinguish between the yellow 
till and the blue, of which the former, occupying the upper por- 
tions, has lost its original bluish color, and has asumed a rather 
yellow tint, which frequently shades into a Hght buff, and at 
places yields to a dark brown or a dull red. It is an unstratified 
material, consisting of clays and sands intermixed, and pebbles 
cobblestones and subangular bowlders of about the same rocks 
as enumerated above, while the percentages of the constitutents 
differ in different localities. With them are associated those 
brick red rron accumulations, described above, and elongated, 
white calcareous concretions, which have been sufficiently de- 
scribed by Call in "The American Naturalist," May, 1882, as 
chieflv occurring in the loess. The coarser material is as a 
rule irregularly disseminated through the matrix. In so called 
'"pockets," however, in lenses and strips, interpolated in the till, 
they have assumed stratified structure. 
It is these upper layers of sand and gravels which sep- 
arate the till into at least two members, which, however, have 
nothing to do with the division of the till into blue and yellow 
till, sometimes both members being found to consist of blue till, 
as for instance at Worthing. Here the separating sand and 
gravel stratum is 10 feet thick, while the upper member of the 
till has a thickness of 60 feet, the lower of only 10 feet. In sec, 
35 of Delapre township, N.W. quarter, the till is divided by a 
stratum of sand, only 4 feet thick, into an upper member of 20 
feet yellow till and a lower one of 70 feet blue till, the sands 
in either case yielding no water. The total thickness of the till, 
