368 WATT. 



of that descent being accomplished merely by the 

 atmospheric pressure. Thirdly the counterpoise at 

 the pump-rod was done away, as a mere loss 

 of power, and the piston was now forced up- 

 wards by the steam entering to fill the cylinder. 

 These two great additional improvements only required 

 a communication to be opened by tubes with the con- 

 denser as well as the boiler, and they gave to the 

 machinery its right to be called a steam-engine ; for it 

 now worked more by steam than by air. The upper 

 chamber was kept air-tight by making the piston-rod 

 work in a socket of tow saturated with grease, called 

 the stuffing-box, which also diminished greatly the 

 friction of the rod. 



If Mr. Watt's invention had gone no further than 

 this, we may perceive that it not only increased the 

 power of the fuel fivefold directly, but obtained from 

 the steam as much additional force as could be derived, 

 the limit being only the strength of the materials, 

 within which limit the safety-valve of Papin always 

 enabled the engineer to keep his power. But the three 

 particulars which have been described were not the 

 whole of this great engineer's improvements upon the 

 mechanism of his predecessors. The smooth working 

 of the engine, especially if it be applied to other and 

 finer operations than those of the miner, depends 

 essentially on the accurate position of the piston rod, 

 with whatever velocity moving, and against whatever 

 weight contending. Its motion must be steadily 

 maintained in the same vertical straight line, or 

 in the same horizontal line, or in the same 

 straight line whatever be its direction, without 



