In his dedication of another work to the queen of England in 1614, we find some allusion made to the construction of hydraulic machines. On his return to France he, as we said before, was appointed engineer to Louis XIII., and was doubtless encouraged by Cardinal Richelieu, that great patron of arts and letters. In the castle of Heidelberg we find another instance of the difficulty that exists in uprooting an historical error. There is in the _Galerie des Antiquités_ of this castle a portrait on wood of Salomon de Caus. Above this portrait is exhibited a folio volume of this author, the _Hortus Palatinus, Francofurti_ 1620, apud Joh. Theod. de Bry, with plates. A manuscript note that accompanies this volume, mentions that the letter of Marion Delorme describing the madman of Bicêtre was extracted from the _Gazette de France_ of 3rd March 1834. Is it not singular that Heidelberg still remains in ignorance of the truth respecting this absurd story, and that the extract from the _Gazette de France_ is still permitted to mislead the public? As recently also as the 30th September 1865, at a banquet given at Limoges, M. le Vicomte de la Guéronnière, a senator and a man of letters, who presided, made a speech which was reproduced in the _Moniteur_ and in which he repeats the anecdote of Salomon de Caus and Bicêtre. The newspaper _L’Intermédiaire_, in its 45th number, of the 10th November 1865, designates this persistence in error as inept and stupid. The works of de Caus were held in high estimation among learned men during the whole of the 17th century. He had however been anticipated in the discovery of the application of the power of steam for propelling large bodies. On the 17th of April 1543, the Spaniard Don Blasco de Garay, launched a steam-vessel at Barcelona in the presence of the Emperor Charles V. It was an old ship of 200 tons called _La sanctissima Trinidada_, which had been fitted up for the experiment, and which moved at the rate of ten miles an hour. The inventor of this first steam-vessel was looked upon as a mere enthusiast whose imagination had run wild, and his only encouragement was a donation of 200,000 marevedis from his sovereign. The Emperor Charles no more dreamt of using a discovery which at that time would have placed the whole of Europe at his feet, than did Napoleon I., three centuries later, when the ingenious Fulton suggested to him the application of steam to navigation. It is well known that Fulton was not even permitted to make an essay of this new propelling force in presence of the French Emperor. So then we must date the fact of the introduction of steam navigation as far back as 1543; anterior to Salomon de Caus in 1615, to the Marquis of Worcester in 1663, to captain Savary in 1693, to Dr. Papin in 1696, and to Fulton and others, who all lay claim to the original idea.