406 JAMES WATT. 



Numerical valuations make us appreciate so well the 

 importance of his inventions, that I cannot resist the de- 

 sire to present two more improvements. I borrow them 

 from one of the most celebrated correspondents of the 

 Academy, from Mr. John Herschel. 



The ascent of Mont Blanc, starting from the valley of 

 Chamouni, is justly considered as the hardest work that 

 a man can accomplish in two days. Thus, the maximum 

 mechanical work of which we are capable, in twice twenty- 

 four hours, is measured by transporting the weight of our 

 body to the elevation of Mont Blanc. This work, or its 



% 



equivalent, would be accomplished by a steam-engine in 

 the course of burning one kilogram of coal. Watt has, 

 therefore, ascertained that the daily power of a man does 

 not exceed what is contained in half a kilogram of coal 

 (1 Ib. Avs.). 



Herodotus records that the construction of the great 

 pyramid of Egypt employed one hundred thousand men 

 during twenty years. The pyramid consists of calcareous 



The detent intended to be used in engines having several cylinders, 

 will also figure among the projects of the Soho engineer. He suggests 

 the idea of perfectly water-tight pistons, though consisting entirely of 

 pieces of metal. It was Watt also who first had recourse to mercurial 

 gauges to appreciate the elasticity of the steam, both in the boiler and 

 in the condenser; who imagined a simple and permanent gauge, by 

 the aid of which, and at a glance, the height.of the water in the boiler 

 can be known; and who, to prevent this level from ever varying to an 

 inconvenient extent, connected the movements of the feeding-pump 

 with those of a float, which, when required, was placed in an opening 

 of the lid of the engine's principal cylinder, forming a little indicator, 

 so combined as to show exactly the law of the steam's consumption 

 relative to the piston's position, &c. If time permitted, I would show 

 Watt not less clever, or less fortunate, in his endeavours to improve 

 the boilers, to diminish the loss of heat, and to burn completely the 

 torrents of black smoke that escape from common chimneys, however 

 high they may be carried. 



