Antecedently to the date of this invention, the effect of heat in increasing the elastic force of air was known, and so far as the above description goes, the whole operation might be ascribed to the air by a person having no knowledge whatever of the elasticity of steam. M. Arago, however, who, on the grounds of this passage in the work of De Caus, claims for him a share of the honour of the invention of the steam engine, contends that the agency of steam in this apparatus was perfectly known to De Caus, although no mention is made of steam in the above description, because in the second demonstration above quoted he uses the words, "the violence of the vapour which causes the water to rise proceeds from the said water; which vapour goes out from the cock after the water with great violence." By these words M. Arago considers that De Caus expresses the quality of elasticity proper to the vapour, and that the context justifies the inference, that to this elasticity he ascribed the elevation of the water in the tube C B. There appears to be some uncertainty attending the birthplace of De Caus. In the _Biographie Universelle_ he is said to have been born and to have died in Normandy. M. Arago assigns Dieppe, or its neighbourhood, as his birthplace. There was another engineer and architect, Isaac De Caus, a native of Dieppe, who published a work in folio, entitled "_Nouvelle Invention de Lever l'Eau plus haut que sa Source, avec quelque Machines mouvantes, par le Moyen de l'Eau, et un Discours de la Conduite d'Icelle_." This volume is without a date, but from the nature of its contents it would appear to have been published before the work of Solomon De Caus already cited. The drawings and machines described in both [Pg022] are exactly the same; but the definitions and theorems quoted above on raising water by fire are not given in the work of Isaac. It seems, therefore, that Solomon De Caus re-published, with additions, the work of Isaac De Caus. From the same birthplace being assigned to both these authors, as well as from the similarity of their pursuits, it is likely they were members of the same family, and from their christian names they were probably Jews. The work cited above, was dedicated to Louis XIII., and in the dedication Solomon De Caus calls himself the subject of that monarch; and in the privilege prefixed to the work he is designated, "Our well-beloved Solomon De Caus, master engineer, being at present in the service of our dear and well-beloved cousin, the Prince Elector Palatine, has made known to us," &c.—"we, desiring to gratify the said De Caus, he being our subject," &c. It is therefore certain, whatever may have been the birthplace of De Caus, that he was at least a subject of France. The circumstance of his work being written in French, though published beyond the Rhine, is also an argument in favour of his being a native of that country. GIOVANNI BRANCA, 1629.