1914] 
HASSELBRING—EFFECT OF SHADING 
261 
highest light intensity for each day was assigned the value of 10, 
and the other values were reduced to the same basis. 
These 
figures are given in table II. The relative light values for any one 
day, therefore, are all directly comparable, but the figures for one 
TABLE I 
AVERAGE LENGTHS (IN SECONDS) OF EXPOSURES MADE IN DETERMINING LIGHT VALUES 
OPEN SHADE 
Thee 
Total light Diffuse light Total light Diffuse light 
Dece 12 
8:15- 8:30 A.M 5.330.112 10.66+0.10 8.72+0.10 12.13 0.25 
9:15- 9:30 A.M 3-560.07 6.900. 13 6.22+0.11 9.72+0.13 : 
10:00-10:15 A.M 2.92+0.09 7.58+0.18 4.360. 10 7.31+0.11 
TEOO-11:15 AM..| 2.23-0.05 8.26+0.13 3.29+0.02 9.32=0.12 
12;30- 1:00 P.M..| 2.32+0.06 7.55#0.13 3.06+0.11 9.29+0.10 
1:30- 2:00 PM..| 3.58+0.07 9.67+0.10 5.13+0.07 | 10.48+0.21 
2330- 3:00 P.M. 5.16+0.11 | 12.30+0.23 7,140.19 |. 10.33£0.12 
3:30" 4:00 PM..| 8.70+0.18 | 17.26#0.18 | 11.340.12 | 15.480.34 
4°45- §:15 P.M..| 24.32+0.95 | 60. T3G. GO ia She es 
December 23 
© ees ers ta, $2.07%6.80 Tier a 56.33+1.03 
ee 1G, 0820.80 [77.33 a ee 15.68+0.57 
ee 1.406. 82-1 9.23+0.49 
Ge, ot... 7 OW b fond 3 SEN REE Res SPA 12.52+0.12 
i cg ee ee O.4OS6 48 be ee 8.80+0.50 
Me tS. te. 16. C6e635 0 Tae 13.660. 18 
MI, foe oe an 1. ee ee eee cr 7.84+=0.08 
ARE ee ee G. 440696 8 Se. ses 8.44+0.08 
| SSRs See ie te 6.964%0:08 410 2S eae: 10.56+0.11 
| co th SSS ee eet $4.1000.56 102 eS 21.400. 34 
Oy cs: Sy comes. 661s ees 94.00+0.67 
grpond 25 
-OO A.M : 
ee ee BOCs} 2. 20 bi oe ee Tt. 0074.05 [snc ass vere 
POO AM af Sales ess take io deren caret oe 
besa ee. 3.60+0.07 8.48+0.08 7,120.12 | 11.20+0.10 
Shain ole pe 3-00+0.06 | 10.32+0.14 6.32+0.10 | 11.60#0.20 
eg te alge 2.340.09 6.880. 16 4.76+0.11 7.820.07 
sch ie... 2.040.05 6.920. 16 3.60+0.08 8.16+0.08 
oe Pees. 2.480.05 7.68+0.09 4.00+0.06 8.56+0.16 
eM, 3.52+0.08 10.08+0.12 440.10 | I1.35#0.17 
3:00 P.M Bese 5.600. 21 13.120. 29 8.120.090 14.680. 22 
OoPm. 7-20+0.09 20.00+0.30 15.480.26 |. oe. ee 
Shimer gree 
day are not directly comparable with those of another day, since 
®r each day a different number was taken as the unit. This 
system was adopted since it was not the purpose to compare the 
light values of the different days, but only those within the cheese- 
loth tent with those outside. : 
