98 IMPROVEMENTS IN STEAM ENGINES. 



weighs near 3 tons, and to open the opposite valve against the 

 momentum of such a column, gives the engine a shock that 

 seems to endanger every part of it. In endeavouring to work 

 with its full power at a speed of 20 strokes a minute, this 

 shock is so severe, as to occasion a very perceptible stop in the 

 return of the stroke, during which the water of condensation 

 mounts into the cylinder. Two methods were proposed to 

 remedy this inconvenience, which amounts to a perfect use- 

 lessness of more than 4. of our power. 1st, to place a large 

 plug-valve E, Fig. 9, in the rising pipe close to the pump, 

 having as much water-way through its seat at a very small 

 rise, as the whole pipe. This valve would shut instantane- 

 ously at the end of the stroke, catching the falling column of 

 water, and nothing would oppose its immediate return. 2d, to 

 place an air-vessel so as to act on the whole column. By 

 this means the fall of the water would be entirely prevented. 



I regret that though this apparatus was provided, and could 

 easily have been put up, in the course of a few days, circum- 

 stances prohibited the trial of them, and that I can only sub- 

 mit them as projects. — Could this pump be used with the same 

 speed as the single pump, one half of the power of every 

 double pumping engine, which works a single pump, would 

 be saved; for the beam would need no counterpoise, and all 

 the expense and friction of a second pump, where two 

 are employed to balance each other, would be avoided. 



I hope shortly to deliver you a second report on this 

 subject, — and am with true respect yours. 



Read May 20th, 1803. B _ HENRY LATROBE. 



Since the above was read in the Society I have constructed 

 another and much larger iron boiler on this plan, the former 

 having fully answered my expectation. In the new boder 

 I have passed the fire through a second flue above the other, 

 which is immersed in the steam only, from which I promise 

 myself great advantage. B. II. L. 



The wooden boiler above described was planned and the erection of it commenced in 

 July, 1801. The cast-iron boiler was projected in the latter end of January 1803. 



