, a jointed pipe is introduced,
formed of wood in Artois, but in other countries more commonly of metal.
It frequently happens that, after passing through hundreds of feet of
retentive soils, a water-bearing stratum is at length pierced, when the
fluid immediately ascends to the surface, and flows over. The first rush
of the water up the tube is often violent, so that for a time the water
plays like a fountain, and then, sinking, continues to flow over
tranquilly, or sometimes remains stationary at a certain depth below the
orifice of the well. This spouting of the water in the first instance is
probably owing to the disengagement of air and carbonic acid gas, for
both of these have been seen to bubble up with the water.[304]

At Sheerness, at the mouth of the Thames, a well was bored on a low
tongue of land near the sea, through 300 feet of the blue clay of
London, below which a bed of sand and pebbles was entered, belonging,
doubtless, to the plastic clay formation; when this stratum was pierced,
the water burst up with impetuosity, and filled the well. By another
perforation at the same place, the water was found at the depth of 328
feet below the surface clay; it first rose rapidly to the height of 189
feet, and then, in the course of a few hours, ascended to an elevation
of eight feet above the level of the ground. In 1824 a well was dug at
Fulham, near the Thames, at the Bishop of London's, to the depth of 317
feet, which, after traversing the tertiary strata, was continued through
67 feet of chalk. The water immediately rose to the surface, and the
discharge was about 50 gallons per minute. In the garden of the
Horticultural Society at Chiswick, the borings passed through 19 feet of
gravel, 242-1/2 feet of clay and loam, and 67-1/2 feet of chalk, and the
water then rose to the surface from a depth of 329 feet.[305] At the
Duke of Northumberland's, above Chiswick, the borings were carried to
the extraordinary depth of 620 feet, so as to enter the chalk, when a
considerable volume of water was obtained, which rose four feet above
the surface of the ground. In a well of Mr. Brooks, at Hammersmith, the
rush of water from a depth of 360 feet was so great, as to inundate
several buildings and do considerable damage; and at Tooting, a
sufficient stream was obtained to turn a wheel, and raise the water to
the upper stories of the houses.[306] In 1838, the total supply obtained
from the chalk near London was estimated at s