Such sporadic experiments as these have no sequential connection with the story of the evolution of the steam engine. The experiments which led directly on to practical achievements were not begun until the seventeenth century. In the very first year of that century, an Italian named Giovanni Battista della Porta published a treatise on pneumatics, in which the idea of utilizing steam for the practical purpose of raising water was expressly stated. The idea of this inventor was put into effect in 1624 by a French engineer and mathematician, Solomon de Caus. He invented two different machines, the first of which required a spherical boiler having an internal tube reaching nearly to the bottom; a fire beneath the boiler produced steam which would force the water in the boiler to a height proportional to the pressure obtained. In the other machine, steam is led from the boiler into the upper part of a closed cistern containing water to be elevated. To the lower portion of the cistern a delivery pipe was attached so that water was discharged under a considerable pressure. This arrangement was precisely similar to the apparatus employed by Hero of Alexandria in various of his fountains, as regards the principle of expanding gas to propel water. An important difference, however, consists in the fact that the scheme of della Porta and of de Caus embodied the idea of generating pressure with the aid of steam, whereas Hero had depended merely on the expansive property of air compressed by the water itself. While these mechanisms contained the germ of an idea of vast importance, the mechanisms themselves were of trivial utility. It is not even clear whether their projectors had an idea of the properties of the condensation of vapor, upon which the working of the practical steam engine so largely depends. This idea, however, was probably grasped about half a century later by an Englishman, Edward Somerset, the celebrated Marquis of Worcester, who in 1663 described in his _Century of Inventions_ an apparatus for raising water by the expansive force of steam. His own account of his invention is as follows: