558 On the Force of Steam or Vapour 
Thus it appears that a ratio having a uniform 
decrease nearly takes place; and we may there- 
fore extend the table of forces at both extremes, 
without the aid of experiment, to a considerable 
distance. Thus, assuming the ratios for each 
interval of 11°F below 32° to be, 1. 500, 1. 515, 
I. 530, 1. 545, &c. and foreach interval above 
212° to be 1.235, 4. 220, 1. 205, 1. 1905 
1.175, 1.160, 1.145, 1.130, &c. we can 
extend the table many intervals of temperature, 
and determine all the intermediate degrees by 
interpolation. This method may be relied upon 
as a near approximation; however it does not 
supersede the expediency of determination by 
experiment; though that is much more difficult 
above 212°, and below 32°, than in the inter- 
mediate degrees: because it is dfficult to procure 
a steady heat above 212°; and below 32° the 
variation of force becomes so small as to elude 
_ minute discrimination. It will appear from what 
follows that the extension of the table by this 
method above 212° is in all probability accurate, 
or very nearly so, for 100° or more, 
