8 SATURATED STEAM, AND OTHER VAPORS. 



The results from Equation C are quite satisfactory ; for the errors come in 

 the ninth place of decimals, and one place of decimals is unavoidably lost 

 In the application of the formula. Equation B was calculated after Equation 

 C and the numerical work was not carried to so large a number of deeimal 

 places. For the calculation of tables, the constants are carried to seven |la< -i * 

 of significant figures only; this gives six significant' figures in the result, ot 

 \\hirh five are recorded in the table. 



Pressure of Steam at Latitude 45. French System. It is customnn t<> 

 reduce all measurements to tin- latitude of 45, and to sea-level. The st.-md- 

 ard thermometer should then have its boiling and freezing points determined 

 under, or reduced to such conditions. The value of 0, the acceleration due 

 to gravity, is, at Paris, latitude 48 50' 14" and 60 metres above sea-l- \< !. 

 9.809218 metres ; and at 45, and at sea-level, it is 9.80605G metres. Con- 

 sequently, 760 mm. of mercury at 45 gives a pressure equal to that of 

 >5 mm. at Paris; and this corresponds to a temperature of 99.'.' 



In other words, the thermometer which is standard at -I.V has each degree 

 0.99991 of the length of the degree of a thermometer standard at Paris. 



To reduce Equation B to 45 latitude, we \\ 



. . .i' . ntgggnt j-rfimam 



log p = a + log jgg-jggg - 6a + c/3; 

 and for Equation <7, 



log p = a + log - 6.- + ^ - 



The resulting equations which were used in calculating Table III are 



B. For steam from to 100 C. at 45 latitude. 



log p = a, - 604" + eft-. 



aj = 4.739502. 

 log b = 0.6117400. 

 log c = 8.13204 - 10. 

 log (4 = 9.996725828 - 10 

 log ft = 0.0068G-I1. 



n = t. 



C. For steam from 100 to 220 C. at 45 latitude. 



log p = a, - 6 l0l " + Cjft". 



aj = 5.457570. 

 log 6, = 0.4r.'"(i-ji. 

 log Cl = 7.74HJ* _ 10. 



log a, - n.ii7nr."J6 - 10. 

 log ft = 0.0076418. 

 n = t - 100. 



