Evaporation from a Circular Water Surface. 317 



evaporation as calculated from the equation 



E = 0'0101a 169 , 



the constants of which equation were obtained graphically, 

 as described above. The last column gives the percentage 

 errors, and it will be seen that the average error neglecting 

 sign is less than 1*5 per cent. In this Table, and in all cases, 

 d stands for the depth of the liquid surface below the rim 

 of the. containing vessel. 



Table I. 



Mean height of barometer =29*6 ins. (steady). 



Max. temp. =18°'8 C. Min. temp. =17°-7 C. 



Relative humidity =63 per cent. 



d=0'7 cm. K = 0-0101. n=l'69. 



a 

 (cm.). 



Loa: a. 



1-0073 

 0-9170 

 08470 

 0-7664 

 0-6990 

 0-6415 42 

 0-5922 42 

 0-5185 I 42 

 0-4533 I 42 

 0-3181 ' 42 



43" 



43 

 42 

 42 

 42 



4m 







58 

 54 

 53 

 54 



58 

 59 

 59 

 58 



Loss in 

 weight 

 (grams). 



LogE 

 (obs.). 



E 



(obs.). 



E 



(calc). 



Per cent, 

 error. 



22-10 



1-7103 



0-5133 



0-5064 



-1-34 



15-15 



1-5470 



0-3524 



0-3579 



4-1-56 



11-90 



1-4424 



0-2770 



0-2727 



-1-55 



860 



1-3021 



0-2C04 



0-1989 



-0 75 



C»-45 



1-1774 



0-1504 



0-1530 



4-1-73 



5-25 



1-0878 



0-1224 



0-1224 



±0-00 



4-373 



2-9977 



0-0995 



0-1011 



+ 161 



3-280 



2-8835 



0*0705 



0-0758 



-0-91 



2-422 



2-7510 



0-0564 



0-0589 



4-4-43 



1-484 



2-5384 



0-0345 



0-0348 



4-0-87 



Average error regardless of sign =1*47 per cent. 



The second table gives a condensed view of all the experi- 

 mental work carried out in the summer. Experiments under 

 the heading A were made under dark-room conditions; those 

 labelled B and C were made in the general laboratory and 

 in the open air respectively. (In the experiments labelled 

 A 3 and A 4 a maximum and minimum thermometer was not 

 used, and the mean is the result of several readings during 

 the course of the experiment). The values of K and n given 

 in the last two columns were obtained, as explained, by 

 graphical calculation. 



Phil. Mag. S. 6. Vol. 34. No. 202. Get. 1917. Z 



