45 



Por Coleman the sunshjr.e record is inooniplete , but the two 

 graphs generally agree in aireotion of slope so far as 

 comparison is possible, excepting between the periods begin- 

 ning July 17 and July 51, ?or Easton Bnd Princess Anne, the 

 curves are typical. Svaporatiori data are lacking for the 

 periods beginning .June 8 and Jiir.e ?3 at th"' latter station. 



The conparatively close agreement, in their main 

 characteristics, between the corresponding .graphs for sunshine 

 and evaporation, for all the sta-^ions employed in this study, 

 together with the fact that the latter graph exhibits no irell- 

 defined relation to the grap'". of temperature efficiency appears 

 to indicate that the rate at which water evaporaed from the 



A 



white cylindrical cups employed as atmometers in this inves- 

 tigation was determined to a considerable extent by the amount 

 of radiant energy absorbed by the cups and that the air tem- 

 perature played a secondary rjart in the determination lT tills 

 rate. The fact that the physiological temperature coeffi- 

 cient is used for expressing temperature does not operate 

 against this conclusion since, as has been -oreviously st.3ted, 

 other methods of expressing temperature give curves which 

 slope for the most part, in the s me direction as the curve of 

 phjrsiologj cal temperr.tare indices. A large effect oi sunshine 

 on evaporation, the sunshine being measured by a black bulb 

 sunshine recorder, has been found by Briggs and 3hantz 

 These authors v;ere able to calculate approximately the amount 



V Griggs, li. J., and Shantz, H. L. , Hourly transpiration 

 rate on clear daj^'s as determined by cyclic environmental 

 factors. Jour. Agrlc. Res. 5:583-650.1916. 



