258 CHAP. XXVII. SIMULTANEOUS VARIATION OF FACTORS 



III. Two Variables : Light and C0 2 -Concentration ; 

 Light carried through Half a Cycle 



In these experiments the change in C0 2 -concentration is 

 from 3 mg. to 7 mg. ; light in each case was carried through 

 half a cycle l x , l 2 , l z . 



(a) l x = 500 lux, c — 3 mg. : activity = 108 -o c.mm. O 



(b) l 2 = 750 „ c = 3 „ : „ = 164-4 » 



(c) l z = 1000 „ c = 3 „ : „ =219-0 

 From the above we find that 



A 5oo : A 75o : A iooo : : Io8-0 : l6 4'4 = 219-0 



: : 2-00 : 3-04: 4-05 



Thus the activities were very nearly proportional to the 

 intensities of light. 



The experiment was repeated with increased C0 2 -con- 

 centration of 7 mg. per 100 c.c. 



activity = 217-4 



= 327-4 

 = 435-3 



(d) l x = 500 lux, C = 7 mg. 

 {e) l % =750 „ C = 7 „ 

 (/) h = 1000 „ C = 7 „ 



Altogether the above results form about eighteen com- 

 binations which supply evidence of the validity of the Law 

 of Product. Of these we will consider in detail two repre- 

 sentative examples : 



Example 1. — From (a) and (b) we obtain the partial 

 effect of light, C0 2 -concentration being constant. 



Activity at 750 lux _ 164 • 4 _ , > 



Activity at 500 lux 108 -o~ • 



The results (a) and (d) give the partial effect of C0 2 -concen- 

 tration, light being constant. 



Activity for 7 mg. C0 2 -concentration_2i7'4_ . » 



Activity for 3 mg. C0 2 -concentration — 108 • ^ ' 



Theoretical increase calculated from product of partial 

 factors (1) and (2) : 



1-52 X 2*0 X original activity 108 -o = 328-3 c.mm. O 



Observed value (e) = 327-4 ,, 



