33^ Literary and Philosophical Society, 



* The above velocity will be found equal to produce the 

 atmospheric pressure, whether the particles strike each 

 other before they arrive at the sides of the cubical vessel, 

 whether they strike the sides obliquely, and, thirdly, into 

 whatever number of particles the 36*927 grains of hydrogen 

 are divided. 



'If only one-half the weight of hydrogen, or i8'4635 

 grs., be enclosed in the cubical vessel, and the velocity of 

 the particles be as before, 6,225 f^^t per second, the pres- 

 sure will manifestly be only one-half of what it was 

 previously ; which shows that the law of Boyle and 

 Mariotte flows naturally from the hypothesis. 



' The velocity above-named is that of hydrogen at the 

 temperature of 60° ; but we know that the pressure of an 

 elastic fluid at 60° is to that at 32° as 519 is to 491. 

 Therefore the velocity of the particles at 60° will be to 

 that at 32° as a/ 5 19, 'v/491 ; which shows that the velocity 

 at the freezing temperature of water is 6,055 ^^^t per 

 second. 



* In the above calculations it is supposed that the par- 

 ticles of hydrogen have no sensible magnitude, otherwise 

 the velocity corresponding to the same pressure would be 

 lessened. 



' Since the pressure of a gas increases with its temper- 

 ature in arithmetical progression, and since the pressure is 

 proportional to the square of the velocity of the particles, 

 in other words, to their vis viva, it follows that the absolute 

 temperature, pressure, and vis viva are proportional to one 

 another, and that the zero of temperature is 491° below 

 the freezing point of water. Further, the absolute heat of 

 the gas, or, in other words, its capacity, will be represented 

 by the whole amount of vis viva at a given temperature. 



