CAPTIVE MOLECULES 



as is known, until the time of the great Italian, Leonardo 

 da Vinci, who, late in the fifteenth century, gave a new 

 impulse to mechanical invention. Leonardo experi- 

 mented with steam, and succeeded in producing what 

 was virtually an explosion engine, by the agency of 

 which a ball was propelled along the earth. But this 

 experiment also failed to have practical result. 



BEGINNINGS OF MODERN DISCOVERY 



Such sporadic experiments as these have no sequential 

 connection with the story of the evolution of the steam 

 engine. The experiments which led directly on to 

 practical achievements were not begun until the 

 seventeenth century. In the very first year of that 

 century, an Italian named Giovanni Battista della 

 Porta published a treatise on pneumatics, in which the 

 idea of utilizing steam for the practical purpose of 

 raising water was expressly stated. The idea of this 

 inventor was put into effect in 1624 by a French en- 

 gineer and mathematician, Solomon de Caus. He in- 

 vented two different machines, the first of which re- 

 quired a spherical boiler having an internal tube 

 reaching nearly to the bottom; a fire beneath the boiler 

 produced steam which would force the water in the 

 boiler to a height proportional to the pressure obtained. 

 In the other machine, steam is led from the boiler into 

 the upper part of a closed cistern containing water to be 

 elevated. To the lower portion of the cistern a de- 

 livery pipe was attached so that water was discharged 

 under a considerable pressure. This arrangement was 



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