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 _ 0.0077 

 -- 



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 n. 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. 



