QUATERNARY DIVISION. 
147 
as there are no clay beds or other strata that are impervious to water above the gravel beds, 
except over small areas, the water could not be expected to rise and overflow permanently. 
The borings for artesian wells are most likely to be successful, where the strata are very slightly 
inclined, and gradually dip down towards the place of boring, from higher grounds, in at least 
one direction, with no deep valleys near, that intervene. In such situations, unless the rocks 
be pervious to water, as open grained sandstones, limestones- or other rocks with, many open 
fissures, the borings will generally be successful. 
The water beneath great cities becomes contaminated by the various animal matters that 
filter into the soil, so that no long period has elapsed before it has been found necessary to 
bring water from a distance by aqueducts, except where it could be obtained to overflow in 
artesian wells from-, a great depth. Nearly all the principal cities of Europe, both ancient and 
modern, were and are supplied by water brought from a distance ; and although little more 
than two centuries have elapsed since the first settlements were made on the Hudson, the 
water of the wells of several of the cities has become so impure, from saline, animal, and de¬ 
composing vegetable infiltrations, that it was not potable, and the inhabitants have obtained 
water from a distance, actuated by considerations of health and comfort. Albany is supplied 
with water from the Patroon’s creek; Hudson, from a limestone spring on Becraft’s moun¬ 
tain ; and the city of New-York, from the Croton river, by an aqueduct 32'88 miles in length. 
The reservoir contains 500,000,000 gallons of water, above the level at which the aqueduct 
will discharge 35,000,000 gallons per day.* The supply is deemed amply sufficient; as the 
daily supply will be more than a barrel of water to each individual, if the city contained a 
million of inhabitants. This is one of the noblest works of ancient or modern times; and 
although mostly concealed below the surface of the earth, so that the obstacles overcome in 
its accomplishment can scarcely be appreciated, yet it is constructed in such a manner as to 
endure for untold ages of time, and to be an honor to the city that authorized it, and to the 
engineers who have planned and executed the work.f 
Valleys are formed in the quaternary deposits, on some parts of Long island, and in many 
parts of the Hudson valley, by the effects of small streams cutting away the clay and sand 
beds ; by springs undermining beds of these materials, and allowing them to sink ; by making 
quicksands, which flow off and carry the superincumbent materials ; or by making clay beds 
slippery, so that if the beds incline, even in a very slight degree towards lower ground, and 
a valley, ravine or bank occurs, so that they are not supported in that direction, they slide off. 
Small sinuous valleys are frequenly formed by springs flowing from or over quicksand beds. 
This is well illustrated on the north shore of Long island. At Roanoke point, and in that 
vicinity north of Riverhead, beds of clay and sand overlie the drift, and the tertiary clays and 
sand underlie the same deposit. The springs cause the sands to flow, and render the clay 
beds slippery, so that the cliffs crack off and slide down on the shore, where the finer parts 
"Introduction to the Natural History of New-York, Vol. 1, Part 1, p. 144. 
t The cost of the Croton aqueduct is about $12,000,000 (Idem, p. 145.) 
