12 MAC Leod, The Place of Science in History. 



The steam engine is an apparatus designed to trans- 

 form heat into mechanical energy, and in which the 

 active medium is steam. The most ancient machine in 

 which the force of expansion of steam was utilised is 

 perhaps the steam cannon invented by Archimedes during 

 the siege of Syracuse (214 — 212 B.C.), but we only possess 

 very vague indications of its nature. 



Almost eighty years later — about 130 B.C. — in the 

 Pneumatica of HERO of Alexandria, a description of the 

 ceolipile was given, a machine which consisted in a hollow 

 sphere revolving on a hollow pillar and provided with two 

 tubes bent in opposite directions and placed at the two 

 opposite extremities of the diameter perpendicular to the 

 axis. The steam, supplied from a boiler, was led through 

 the hollow pivot and escaped through the bent tubes, the 

 sphere turning by the reaction. It was fundamentally, 

 as is easily seen, a primitive turbine. 



During the seventeen centuries which followed no 

 notable progress was made. One step forward was 

 however registered by GIOVANNI BAPTISTA DELLA 

 Porta. In his Treatise on Pneuma 'tics, which appeared in 

 1 60 1, is to be found the description of an apparatus 

 constructed as follows. It consists in a sealed vessel 

 containing water and provided with two tubes. One of 

 'them communicates with a boiler in which steam is 

 generated, the other passes into the water and communi- 

 cates with the exterior. The pressure exercised by the 

 steam on the water makes it spout out of the open tube. 

 The inventor demonstrated that the condensation of the 

 water vapour in the sealed vessel, after the water had 

 been driven out, could be utilised to produce a vacuum to 

 draw up water from a lower level. 



In 161 5 Salomon de Caus described a fountain 

 similar to that of della Porta but composed only of a 





