Daniel Bernoulli, in the year 1753, proved on paper that it was mathematically possible to use a steam engine for propelling ships, the medium being also wheels with vanes attached. There were not wanting other theories and experiments also in the eighteenth century which attained little or no success, their defects arising sometimes through lack of sufficient power to go against a stream, or through some erroneous principle. Of these we might mention especially the experiment made in France by Périer, who, after devoting careful consideration to the problem of the amount of power required, and, after reckoning the necessary force likely to be essential, by the number of horses which were required for drawing along a boat from the towing-path, set to work in his own manner. It happened that in the year 1775, to which we are now referring, there was on view in Paris a unique engine which the now famous and ever memorable James Watt had made. This aroused so much interest that it was decided to hire a boat on the Seine and place therein a Watt machine of one horse-power. Périer carried out his experiment, though owing to the force of the current of the Seine, and the too limited horse-power which the engine was capable of producing, the result was a failure. But one of Périer’s associates, the Marquis de Jouffroy, had also been excited by the advent of this English engine which was an improvement on anything that the world had yet seen, and he resolved to try for himself to find some means of making a ship to go against swift-running rivers independent of horse-towage. In spite of the prejudice which was likely to be aroused in case he should prove successful (for the owners of the monopoly of the more primitive form of inland water transport would not quietly consent to see their living taken away from them), he set forth with considerable courage and an heroic determination. Since it is doubtful whether these interesting experiments would ever have been made had it not been for the happy coincidence of Watt’s engine becoming known when it did, it is only right that we should first see something of the circumstances which combined to bring the Englishman’s work into such prominence, and then return to follow de Jouffroy in his efforts.