The publication of Papin’s correspondence with Leibnitz puts the case beyond all possibility of doubt, and the reader who cares to pursue the subject will find the facts he requires in “Leibnizens und Huygens’ Briefwechsel mit Papin,” by Dr. Ernst Gerland. From this we see that Papin had already published a treatise dealing with the application of heat and water. In a letter, dated March 13, 1704, he wrote to Leibnitz of his intention to build a boat which could carry about four thousand pounds in weight, and expressed the opinion that two men would be able to make this craft easily and quickly to ascend the current of a river by means of a wheel which he had adjusted for utilising the oars. That Papin made no aimless plunge, but went into the matter scientifically, is quite clear. He studied carefully the important fact of the resistance which is offered to a vessel passing through the water, and thus found what he believed to be the correct lines on which his ship was to be built. He shows that he had been hard at work expanding his theories, and was longing to have the opportunity to put them to a practical test. On July 7, 1707, he writes to say that he has many enemies at Cassel (where he was then sojourning) and contemplates going to England; and in asking permission so to do he brings forward the plea that it is important that the new type of ship should have a chance of proving its worth in a seaport such as London. He does not conceal the great faith which he reposes in this novel craft: “_qui, par le moien du feu, rendra un ou deux hommes capables de faire plus d’effect que plusieurs centaines des rameurs_.” Then, writing again to Leibnitz, also from Cassel, under date of September 15 of the same year, relating the result of his experiment of this first steamboat, he remarks: “_Je Vous diray que l’experience de mon batteau a êté faitte et qu’elle a reussi de la manière que Je l’esperois: la force du courant de la riviere ètoit si peu de chose en comparaison de la force de mes rames qu’on avoit de la peine à reconnoitre qu’il allât plus vite en dêcendant qu’en montant._” With such statements as these before us, we can no longer be in any doubt as to the first author of the steamboat.