a part of the water in which it is immersed will rush into it by the valve _u_, and occupy the whole internal cavity, thus putting it in a state of preparation for a second opening of the cock _z_, by which its contents will be again discharged into the cistern _y_, and so of the two vessels alternately; for while _v_ is emptying, _t_ will be filling, and vice versâ, which agrees with the Marquis's account when he says, "that the man is but to turn two cocks, that one vessel of water being consumed, another begins to force," &c. The above suggestion for an engine capable of raising water may be still further improved by adding a suction pipe to the valves _u_ _u_, and the pressure of the atmosphere will increase the working power of the engine more than thirty feet: and should a less height be required, the forcing pipe may be shortened in a proportionate degree: indeed this fact was attended to by the next person who claims the honour of having invented the steam-engine, to which it may now be adviseable to direct the reader's attention. [Illustration] The engine suggested by Savery for the purpose of raising water, consisted of a boiler _a_ furnished with a safety valve _v_. The steam-vessel _r_ was connected with the well H, by a suction pipe _n_; and when water was to be raised the vessel _r_ was filled with steam, which rushing in, soon expelled the air: when that was completely effected, the communication with the boiler was closed, and the steam condensed, which diminishing its bulk, formed a vacuous space within the vessel; the pressure of atmosphere then operating upon the surface of the water in the well, drove it up the pipe. In this form of the apparatus, the inventor was seldom able to raise water more than thirty feet: and when a greater altitude was required, it was effected by the impellent force of high pressure steam. This was accomplished by the ascending pipe _k_, which was sometimes carried sixty feet higher than the steam-vessel _s_; and a reference to the great expansive force of steam will show that this operation must be attended with considerable danger. After condensing the steam and filling the vessel _r_ with water, a new supply of steam was then introduced, which pressing on the surface of the water, drove it up the pipe _k_; and it will be evident that the pressure on the internal surface of the boiler must be proportioned to the height of the column of water thus raised by the steam. The principal objection to this form of the engine arises from the great consumption of fuel, a considerable portion of the caloric employed in the generation of the steam being absorbed in heating the new surface of cold water last raised from the well; and where great heights are required, there appears no mode of completely obviating this objection. Should it, however, be required merely to raise water about thirty feet, there are few contrivances more economical or better adapted for general use.