HISTORY OP PROPELLANTS 29 



wide differences of opinion were entertained by the many 

 eminent men who iiave written upon the subject. 



De la Hire, the first writer on gunpowder, in 1702, sup- 

 posed that the propelling force of gunpowder was due to 

 the elasticity of the air between the grains, and that the 

 function of the powder was merely that of a heating agent. 



Robins, however, who in 1743 read before the Royal 

 Society of London a paper in which he described his exper- 

 iments, pointed out that he had found that at ordinary 

 temperatures and atmospheric pressure the generated gas 

 occupied about 236 times the volume of the gunpowder, 

 and that at the temperature of explosion which, however, 

 he much underestimated the maximum pressure would 

 be about 1,000 atmospheres (6.6 tons per square inch). 



He considered, and cited experiments to prove, that the 

 whole of the powder he employed must be fired before 

 the projectile was sensibly moved from its seat, his argu- 

 ment being that, were this not so, a much greater energy 

 would be realized when the weight of the projectile was 

 materially increased ; but this experiment showed that this 

 was not so. 



Hutton, in 1778, read before the Royal Society an ac- 

 count of his celebrated researches in gunnery, and detailed 

 the experiments from which he deduced the maximum 

 pressure of gunpowder to be about twice that given by 

 Robins, or about 2,000 atmospheres. 



Hutton, like Robins, saw that the energy of gunpowder 

 was due to the elasticity of the highly heated gases gener- 

 ated by the explosion and, assuming that the powder was 

 instantaneously ignited and that the pressure was as he 

 stated, gave formulae for deducing the pressure of the gas 

 and the velocity of the projectile at any point of the bore. 



In 1797 Count Rumford communicated to the Royal 

 Society his celebrated experiments on gunpowder, and 

 these remained for many years the only experiments from 

 which the pressure was deduced by actual measurement. 

 In Rumford 's case the weight lifted by the pressure of the 



