Geoscience Reference
In-Depth Information
experiment and of field observations similar to Seneca's. By today's standards and with
present understanding of the underlying physics, his interpretation of these observations
was wrong. The reason for this was Perrault's inability to grasp the effects of surface ten-
sion on the flow of water in a partly saturated soil. Clearly, the time was not ripe yet and
a satisfactory explanation of his column experiment and his field observations would only
be possible some 200 years later in the nineteenth century. In any event, whatever damage
may have been caused by Perrault's topic was soon undone by the more fundamental and
perceptive work of Mariotte.
Mariotte's reaffirmation and proof of the Common Opinion
Few facts are known with certainty about the life of Edme Mariotte (Picolet, 1986). He was
born around 1620 in Til-Chatel (or Tilchatel) near Dijon in Burgundy and died in Paris in
May 1684; he appears to have spent most of his early life in Burgundy, probably until 1666,
when he was elected one of the original members of the newly founded Academie Royale
des Sciences (de Condorcet, 1773) and he had to move to Paris. By 1634 he had received
tonsure and was therefore a cleric, but there is no evidence that he received higher orders
or was ever ordained into the priesthood. Perhaps as early as 1634 he was also appointed
prior of St. Martin de Beaumont-sur-Vingeanne, which provided an annual income of some
300 pounds. But this did not involve major responsibilities and his life was essentially
devoted to science. While he had many diverse interests (see Davies, 1974), he is now
remembered mostly for the law of gases that bears his name, his discovery of the blind spot
in the human eye, and his work on the laws of impact between bodies, among many other
contributions. A fine example is the constant head device shown in Figure 9.2, which to
this day is called a Mariotte flask. As member of the Academie he was also involved in the
hydraulic works for the fountains at the king's new castle in Versailles. But it is his major
work on this subject, namely
Treatise on the Movement of the Waters and of the Other Fluid
Bodies
(Mariotte, 1686), published posthumously, which is of interest here. In the section
“On the origin of springs,” he first treats the formation of rains, and then unambiguously
specifies what happens next (p. 19)
Having fallen, the rains penetrate the earth through little channels which they find there; thus, when
one digs somewhat deeply into the earth, one usually encounters these little channels, whence the
water, which gathers at the bottom of what one has excavated, makes the water of wells; but the water
of the rains, which fall on the hills & on the mountains, after having penetrated the surface of the
earth, mainly where it is light & mixed with pebbles & roots of trees, often encounters clayey soil or
continuous rocky formation, which it cannot penetrate and along which it flows to the bottom of the
mountain or some considerable distance from the summit, where it comes out again into the open, &
forms the springs. This effect of nature is easy to prove, because firstly the water of the rains falls all
year long in sufficiently large abundance to maintain the springs & the rivers, as we shall show later on
by calculation; secondly, we observe every day that springs increase or decrease according to whether
it rains or doesn't rain; & if two months go by without considerable rain, they decrease most of them by
one half; & if the drought continues for another two or three months, most of them dry up & the others
decrease down to one quarter. From this one may conclude that if there were a whole year without
rain, there would be very few springs left, most of which would be very small, or that they would cease
altogether.
With his own view clearly explained, Mariotte proceeds in detail to refute some of the
mechanisms proposed by others and to provide proof of his own assertions. He first deals
with those philosophers who assume that vapors rise from the depths of the Earth to condense
into water inside the mountains when they encounter the upper vaults like in an alembic,
whence the water flows out to form springs. Mariotte rejects this hypothesis by indicating,
