of evaporation froi:; a shallow 'blackeneri tank usj'^'- « formula 

 which involved sunshjne intensity ani tir^e saturation deficit 

 of thedtr, and in vrhich sunshine has a preponderating in- 

 fluence. They also stnte that an approximate proportionalj ty 

 exists "betv/een the loss from the tank and the loss from 

 Livingston '^orous cup atmometers. While the cups and the tank 

 respond in -■! * f f ersnt wajrs to the daily cycle of changes 

 in the evaporating po-,';er of the air, a certain average ratio 

 exists between the evaporation from the tank and the evap- 

 oration from the cups. It 'vould therefore "be exoected from 

 their work that e aporation from Livingston porous cups would 

 he largely infl-;enGed by sunshine intensity, and that tem- 

 perature would '^how a secondary influence on evaport'o-n as 

 measured by these instruments. It must be remenbered, also, 

 that the evaporation meaaurements of .this experiment were 

 made in the plant enclosures, v.hile temperature was measured 

 by thermometers locate 1 in a shelter abotit 1 l,/2 meters (5 feet) 

 above the ground and often 4 or 5 meters fl5 feet) from the 

 plant enclosures. This ma37 account in some measure for the 

 apparent absence of any marked effect of temperature on the 

 evaporating power of the atr as measured bv porous cup at- 

 m.ometers. 



It m^ be noted here that the temperature efficiency 

 values for tiie various -tat ions here considered, exclusive 

 of Oakland are much more nearly alike for any gi''*^^ two-WT?ek 

 period +-han are the sunshime and evaporation values. The 

 values of these three climatic indices ior the first two weeks 

 of -June and for the first two v/eeks of August, for these 



