54 



[April 3, 



distance of the maximum temperature of saturation the rate of ex- 

 pansion of steam was found to be exceedingly variable ; near the 

 saturation-point it is higher than that of air, and decreases as the 

 temperature is increased, until it becomes sensibly identical with 

 that of air. The results upon which this law was based were too 

 limited in their range for much numerical accuracy in the constants 

 deduced. 



Hence it has been our object in the present paper to supply the 

 deficiency in the previous one, by affording experimental data of the 

 expansion of steam at higher temperatures and with a greater range 

 of superheating than was possible with the apparatus employed in 

 ascertaining the density of steam. The results obtained in these 

 later experiments, however, confirm the general law deduced from the 

 previous ones. 



The figure represents the apparatus used when the pressure did 



