l-'sychroiiK'tric ForiituUi. 165 



,. These figures again show no docided gain in accuracy by the use 

 of the modified formuhi. The sums of the errors taken without regard 

 to sign are 182.34 and 180.98, showing an average error 0.01 less in 

 one case than in the other. Tlie probable errors are respectively 

 1.57 and 1.54, the difference being too small to be significant. 



Wind -effects. 



TTie value 0.00072 for the constant A was derived from observa- 

 tifins taken under all conditions of wind-velocity, no artiticial method 

 of ventilation having been used. Hy gi'ouping the observations in 

 accordance with the strength and direction of the wind, however, the 

 value of the constant is found to vary in the manner generally 

 acknowledged. It is a maximum under calm conditions and decreases 

 as the velocity of the wind rises. From only 11 observations in calm 

 air' A = 0.001)7887, which agrees with the value 0.0007882 from 17 

 obse-rvations of the earlier series (the values given in the former papei 



