20 HEROES OF INVENTION AND DISCO VERY. 



JAMES WATT 



LL the inventions and improvements of recent times, il 

 measured by their effects upon the condition of society, 

 sink into insignificance, when compared with the extraordinary 

 results which have followed the employment of steam as a 

 mechanical agent. To one individual, the illustrious James 

 Watt, the merit and honour of having first rendered it exten- 

 sively available for that purpose are pre-eminently due. Thd 

 force of steam, now so important an agent in mechanics, was 

 nearly altogether overlooked until within the two last centuries. 

 The only application of it which appears to have been made by 

 the ancients, was in the construction of the instrument which 

 they called the ^olipile, that is, the Ball of ^olus The 

 ^olipile consisted of a hollow globe of metal, with a long 

 neck, terminating in a very small orifice, which, being filled 

 with water and placed on a fire, exhibited the steam, as it was 

 generated by the heat, rushing with apparently great force 

 through the narrow opening. A common tea-kettle, in fact, is 

 a sort of ^olipile. The only use which the ancients proposed 

 to make of this contrivance was, to apply the current of steam, 

 as it issued from the spout, by way of a moving force — to 

 propel for instance, the vans of a mill, or, by acting immediately 

 upon the air, to generate a movement opposite to its own 



