Mersenne

Pascal sent copies of his booklet to all his friends in Paris and to every town in France where he thought there were people who might be interested in reading it—presumably, to the local booksellers, for somewhere between fifteen and thirty copies went to Clermont-Ferrand alone; Mersenne sent copies to Sweden, Poland, Germany, Italy, and indeed all over the place.

Descartes was absolutely furious and denied any influence, but when Mersenne visited Beeckman and read his journal he discovered that, indeed, many of Descartes’ ideas had first been formulated by Beeckman.

Pascal always claimed to be the inventor of this experiment, but the philosopher Rene Descartes insisted that he had originally suggested it to Pascal, and their joint friend Marin Mersenne was busy trying to organize the very same experiment when Pascal beat him to it.

This story is normally told as though Pascal was right and Mersenne and Roberval wrong, although actually all three were right: the space was in effect a vacuum, but it did contain some air under extremely low pressure.

The status of experimentation was changing; and Pascal and Mersenne made every effort to bring this about.