Descartes: A Biography

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 Descartes: A Biography

to focus his speculative work apart from the scholastic philosophy that

he had learned at La Fl`eche and the mathematical problems that he had

attempted to solve as a self-taught practitioner.

However, these ambiguities were overshadowed by one clear suggestion

from an unexpected source. In the spring of,anengineer and architect

in the service of the prince elector of Palatine, Salomon de Caus, published

a book entitled:The Explanation of Moving Forces, with various machines,

both useful and decorative; to which are added various designs for Grottoes

and Fountains.This book was reissued and published in Paris in,

prior to its author’s death there in. Although Descartes does not

mention De Caus in his subsequent correspondence, his later adoption of

mechanical models makes it highly likely that he consulted his book during

this period and that it sparked his interest in the possible adaptation of

hydraulic models to his scientific ambitions.

De Caus defines a machine as ‘a combination and firm connection of

timber or other material, which has power and movement either from itself

or from any other source,’ and he distinguishes three kinds of machines:

those for lifting weights, pneumatic machines that are powered by water

or air, and machines such as windmills.He argues, in Book I, that there is

no vacuum in nature – a thesis later defended by Descartes – and he illus-

trates and supports this claim by various examples. The first argument is

that water will not flow out from a container that is filled with water, which

has a hole at the bottom, unless a tap is opened at the top to allow air to

enter and fill the space left empty by the water. There is a similar argument

in reverse, that one cannot pour water into a container that is already full

of air unless the air is allowed to escape through some aperture.

Book II, concerning grottoes and fountains, is dedicated to Princess

Elizabeth, the mother of the princess with whom Descartes corresponded

in thes.This book is divided into ‘problems’, much like engineering

exercises, which are arranged in sequence so that later problems are more

complicated and presuppose the designs provided in previous solutions.

Forexample, the first problem is to ‘design a grotto which includes a satyr

that will play the flageolet, and a nymph that responds to the satyr’s musical

cadences.’Having discussed a wide range of machines, including pulleys

forlifting weights, clocks controlled by a running stream, a water pump

to quench a house fire, and a machine to simulate the singing of a bird, it

is simply the next step of a natural progression to construct ‘a machine

bywhich a Neptune is represented, which turns in a circle around a rock,