164 FERGUSON'S LECTURES.,. 



LECT. at such a distance. But this way hath no bounder ; for I have 

 V. taken a piece of a whole cannon, whereof the end was burst, and 

 filled it three-quarters full of water, stopping and screwing up 

 the broken end, as also the touch-hole, and, making a constant 

 fire under it : within twenty-four hours it burst and made a great 

 crack ; so that, having a way to make my vessels, so that they 

 are strengthened by the force within them, and the one to fill 

 after the other. T have seen the water run like a constant foun- 

 tain stream forty feet high ; one vessel of water rarefied by fire 

 driveth up forty of cold water. And a man that tends the work 

 is but to turn two cocks, that one vessel of water being con- 

 sumed, another begins to force and re-fill with cold water, and 

 so successively, the fire being tended and kept constant, which 

 the self-same person may likewise abundantly perform in the 

 interim between the necessity of turning the said cocks." 



The engine suggested by Savery for the purpose of raising 

 water, consisted of a boiler o, furnish- 

 ed with a safety-valve m. The steam 

 vessel s was connected with the well 

 c by a suction pipe h, and when wa- 

 ter was to be raised, the vessel s was 

 filled with steam, which, rushing in ? 

 soon expelled the air : when that was 

 completely effected, the communica- 

 tion with the boiler was closed, and 



the steam condensed, which, diminishing its bulk, formed a 

 vacuous space within the vessel, the pressure of the atmosphere 

 then operating upon the surface of the water at c, 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 

 the steam. This was accomplished by the ascending pipe a d 

 which was sometimes carried sixty feet higher than the steam 

 vessel s; and a reference to the principle by which it was 

 effected will shew that this operation must be sometimes 

 attended with c n nsiderable danger. After condensing the 

 steam, and filling the vessel s with water, a new supply of steam 

 was then introduced, which, pressing on the surface of the wa- 

 ter, drove it up the pipe d; and it will be evident that the 

 pressure on the internal surface of the boiler must be propor- 

 tioned to the height of the column of water thus raised by the 

 steam. 

 The principal objection to this form of the engine arises froir 



