SECT. II.] 
PROPERTIES OF STEAM. 
59 
Add 100 to the temperature, and divide the sum by 177 ; the sixth power of the 
quotient is the force in inches required. 
Example. To find the force of steam for the temperature 312°. 
312+100 _ 2.3277. 
177 
Raise this to the sixth power, and it gives 159 inches for the force of the steam in 
inches of mercury. 
Or by logarithms. Add 100 to the temperature, and from the logarithm of this 
sum subtract 2*24797 ; and six times the difference is the logarithm of the force 
in inches of mercury. 
Example. To find the force of steam for the temperature 250°. 
Log. (250 + 100=350) is - 2*54407 
Subtract constant log. - 2*24797 
Difference - 0*29610 
6 
Log. of force in inches of mercury = log. 59*79 = 1*77660 
89. Rule ii. The force of the steam of water being given to determine its 
temperature. 
Multiply the sixth root of the force in inches by 177, and subtract 100 from the 
product, which gives the temperature required. 
Example. Let the force of steam be eight atmospheres, or 240 inches of mer 
cury, to find its temperature. 
The sixth root of 240 may be easily found by a table of squares and cubes, by 
first finding its square root, and then the cube root of the square root. Thus the 
square root of 240 is 15*492, and the cube root of 15*492 is 2*493 ; hence, 
(2*493 x 177) — 100=341*20. Mr. Southern’s experiment gives 343*6. 
Or by logarithms. To one-sixth of the logarithm of the force in inches add 
2*24797 : the sum is the logarithm of a number, from which 100 being subtracted 
the remainder will be the temperature required. 
Example. Let the force of steam be equal to sixty inches of mercury, which is 
nearly fifteen pounds on the square inch above the pressure of the atmosphere, to 
find its temperature.