Description of the First Steam. Engine. 41 



ter to condense the steam and fill the vessel efgli, and which 

 will also be forced into this vessel, (by the pressure of the at- 

 mosphere,) to occupy the vacuum effected by the condensed 

 steam. The cock n is next to be turned so as to permit the 

 vessel abed" to force and re-fill with cold water," and, at 

 the same time, the steam cock k is to be turned, so as to per- 

 mit the steam to act upon the surface of the water in the ves- 

 sel efgh, and so on alternately, producing a constant stream 

 from the top of the force pipe. The boiler may be supplied 

 with water from the cistern RS, by means of a small pipe and 

 stop cock. 



To produce " a constant stream forty foot high, one vessel 

 of water rarefied by fire, driveth up forty of cold water, (or 

 in other words, forty times the quantity in the boiler.) A 

 man that tends the work is but to turn two cocks, that one 

 vessel of water being consumed, another begins to force and 

 re-fill with cold water, (by the pressure of the atmosphere,) 

 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." 

 Although the Marquis of Worcester has only proposed to 

 force water by his engine to a great height, yet it appears 

 that he knew that water could have been brought up from a 

 limited depth by suction, (by the pressure of the atmosphere 

 into a vacuum) ; for the G8th article commences with these 

 words : ** An admirable and most forcible way to drive up 

 water by fire, not by drawing nor sucking it upwards, for that 

 must be as the philosopher calleth it, intra sph&ram activi- 

 tatis, (within its sphere of activity,) which is but at such a dis- 

 tance." 



It is therefore very obvious that the Marquis had a know- 

 ledge to what height water could have been raised from the 

 effects of a vacuum, and which he had put a small value upon 

 in comparison of what he had in view ; for he adds, " But 

 this way hath no bounder if the vessels be strong enough." 

 The Marquis a little further on says, " So that having a way 

 to make my vessels, so that they are strengthened by the force 

 within them." 



This can only apply to strengthening his boiler and vessels 



