PHYSICAL FACTOR RESULTS 99 



tained from the ecograph which makes it possible to get the exact mean 

 from the sum of all the hour readings. When it comes to the seasonal 

 mean, the ecograph is even more necessary, exception being made for 

 water-content, in which case a number of readings on various days through 

 the season will suffice. The value of factor means for diagnosis and for 

 curves has already been sufficiently commented upon, and the feasibility of 

 factor sums already indicated. 



