IOWA ACADEMY OF SCIENCES. 27 



ideas of Black soon bore fruit in the improvement of the steam 

 engine by Watt, in 1783. Lavoisier determined the specific 

 heat of a number of substances. 



The mechanical theory of heat was nob known to the philos- 

 ophers and scientists before the eighteenth century. From a 

 speculative point of view, Descartes, Boyle, Bacon, Hooke and 

 Newton all looked upon heat as possibly a mode of motion. 

 Boyle actually experimented upon the mechanical production 

 of heat, but the theory never attained a scientific basis until 

 the nineteenth century, and, in fact, was not established 

 beyond controversy umil about the middle of our century. 



The material theory of heat can be traced to the 

 Greeks. In the early part of the seventeenth century it was 

 advocated by Gassendi; the phlogiston theory of combustion 

 seemed to lend it support. In 1783 the French Academy offered 

 a prize for the best paper on the theory of heat. It was won 

 by Euler, who supported the material view, though he is 

 apparently the only man of the century seriously to advocate 

 the wave theory of light. 



The material theory was not seriously questioned until 

 Count Rumford observed the enormous amount of heat caused 

 by friction, in boring cannon at Munich, in 1798. He su -rounded 

 a piece of brass, in a cavity of which worked a blunt drill, 

 with a box in which he placed eighteen and one- half pounds of 

 water. The drill was started in rotation and at the end of 

 two and one-half hours the water actually boiled. He expresses 

 his delight, and the astonishment of the bystanders, that so 

 much water should be made to boil without any fire. He 

 remarks that the source of heat generated by friction seems 

 inexhaustible. In 1804 he wro e to Pictet, of Geneva, " I am 

 persuade! that I shall live a sufficiently long time to have the 

 satisfaction of seeing caloric interred with phlogiston in the 

 same tomb." But Rumford underestimated the strength of 

 conservatism. The war over the nature of h'^at was to be a 

 long one, and the establishment of the mechanical theory 

 required fifty years, and all the genius of Young, Meyer, Joule, 

 Thompson, Carnot, Clausius and Rankine. 



ELECTRICITY AND MAGNETISM. 



Electricity and Magnetism may be considered together though 

 their relation was discovered by accident by Oersted in 1819. 

 The facts of the existence of magnetism and electricity have 

 been known for ages. Tha founding of magnetism as a branch 



