Mariotte interprets the phenomena as percussions, and in this sense this appraisal is the first appearance of the ‘impact theory’ which we shall presently consider. The question why Mariotte did not follow the experimental method of Huygens is not easy to answer; but we conjecture he was influenced by the fact that the results of the experiment of the jet against a plate were quite uncertain, because he was familiar with water mills and experimented with them on the river Seine, as he mentions in his Traité. To sum up, Mariotte’s contribution rightly merits the qualification of precursor that Dugas awards him.