Geoscience Reference
In-Depth Information
usually assumed about medieval scholarship, Aristotle's theories were not always blindly
accepted but they often provided the impetus for more correct interpretations. The writings
of Buridanus (Jean Buridan,
c
. 1295-1358) from Bethune in Picardy, are a case in point. He
is probably best known for his proverbial ass (asinus) and also for the fact that, in rebuttal to
Aristotle and some 350 years before Newton, he had some idea of the principle of momentum
conservation. In his topic
Questions on the three topics of Aristotle's Meteorologica
(Ducos,
1998, p. 82), Buridanus wrote the following.
For it is also said to be possible that the water of the sea is evaporated and that the vapor is changed
into air, which is carried by the wind to a distant place, and descends there to the earth to replenish the
pores to avoid a vacuum, and is there condensed and changed into water, which comes to the spring
and then flows to the sea.
In this passage he seems to admit that Aristotle's mechanism of condensation inside the
Earth may be possible, but then he continues in direct contradiction of Aristotle, pointing
to the rain as the substantial source of the springs.
The waters of springs come from the rains in this manner, because there are in the earth large hollow
spaces which receive much rain water in winter, which for some hollow spaces suffices to flow out
through the year until the winter rains return, and thus they are perpetual springs, which flow from
these hollow spaces. There are other smaller hollow spaces which cannot receive in themselves so
much water, which would suffice to flow out through the whole year; therefore, the springs which flow
from them dry up in summer.
In other words, if the condensed water could be a substantial source of spring water, springs
would not dry up in summer. This shows that among some influential scholars at the
University of Paris, rain was taken as the main, if perhaps not the sole, agent in the generation
of springs.
Later examples, indicating that the rainfall percolation concept was not uncommon
throughout this period, are the accounts by Bernard Palissy (1510-1589) (Palissy, 1888;
1957) and Guillaume de Salluste du Bartas (1544-1590) (du Bartas, 1988, p. 78). Both
gave descriptions of the origin of springs and rivers that come generally quite close to
the rainfall percolation mechanism as it is known today. It is worth noting that, just like
Vitruvius, neither one was famous for his philosophical ideas; Palissy was known mostly
for his practical and artistic talents as a ceramist, and Bartas, a soldier and diplomat, for his
poetry. Although both were Huguenots, their specific ideas on the origin of springs do not
appear to be literal biblical accounts.
But disagreement with Aristotle among some did not necessarily lead to improved
concepts among others. For instance, Leonardo Da Vinci (1452-1519), in his notebooks
(see MacCurdy, 1938, p. 22) first describes how heat raises water vapor to higher elevations,
where it condenses and falls as rain and hail; he then explains how in a similar way the
same heat also draws up water from the roots of the mountains, through channels inside
these mountains like through the veins inside the human body, to their summits, where the
water can flow out through cracks and crevices to create rivers. He also concludes “. . .
that the water passes from the rivers to the sea, and from the sea to the rivers, ever making
the self-same round...”thus implying the seawater filtration mechanism to arrive back at
the roots of the mountains. Another example is the description given by Descartes (1596-
1650) (1637, p. 179), which was also nearly the same as the seawater filtration theory of old.
Hence, the fresh waters which flow into the sea, do not make it any larger because as many
others leave it continuously. Some of these waters are raised in the air after being changed
into vapors, and then proceed to fall back down as rain or snow on the earth; however, most
