no Experiments to determine 



with the amazing force of steam, when heated only to a 

 few degrees above the boiling point, can easily perceive 

 that its elasticity must be almost infinite, when greatly 

 condensed and heated to the temperature of red-hot 

 iron ; and this heat it must certainly acquire in the ex- 

 plosion of gunpowder. But if the force of fired gun- 

 powder arises ■principally from the elastic force of heated 

 aqueous vapour, a cannon is nothing more than a steam- 

 engine upon a peculiar construction ; and upon deter- 

 mining the ratio of the elasticity of this vapour to its 

 density, and to its temperature, a law will be" found to 

 obtain, very different from that assumed by Mr. Robins, 

 in his Treatise on Gunnery. What this law really is, I 

 do not pretend to have determined with that degree of 

 precision which I wished ; but the experiments of which 

 I am about to give an account will, I think, demonstrate 

 in the most satisfactory manner, not only that the force 

 of fired gunpowder is in fact much greater than has been 

 imagined, but also that its force consists principally in 

 the temporary action of a fluid not permanently elastic, 

 and consequently that all the theories hitherto proposed 

 for the elucidation of this subject must be essentially 

 erroneous. 



The first step towards acquiring knowledge is un- 

 doubtedly that which leads us to a discovery of the 

 falsehood of received opinions. To a diligent inquirer 

 every common operation, performed in the usual course 

 of practice, is an experiment, from which he endeavours 

 to discover some new fact, or to confirm the result of 

 former inquiries. 



Having been engaged many years in the Investigation 

 of the force of gunpowder, I occasionally found many 

 opportunities of observing, under a variety of circum- 



