TEMPERATURE AND LIGHT 259 



Example 2. — The partial effect of light is found from (a) 

 and (c), C0 2 -concentration being constant. 



Activity at iooo lux _ 219 • o _ ,, 



Activity at 500 lux ~~ 108 • o 



From (c) and (/) we obtain the partial effect of C0 2 - 

 concentration, light being constant. 



Activity for C0 2 -concentration 7 mg. _ 435-3 __ , 



Activity for C0 2 -concentration 3 mg. 219 -o - 



Activity for simultaneous change of light and C0 2 - 

 concentration is : 



Calculated result, (3) X (4) X original activity, io8-oc.mm. O 



2-02 x 1-99 x 108= 434-ic.mm. 

 Observed result (/) = 435*3 ,, 

 The Law of Product is fully verified by these facts, which 

 prove once more that 



— is a constant. 

 LC 



IV. Two Variables : Temperature and Light ; 

 Temperature carried through a Cycle 



Though the experimental difficulties involved in producing 

 more numerous and complex combinations are formidable, 

 yet the results already obtained were so uniformly consistent 

 that I ventured to subject the applicability of the Law of 

 Product to a yet severer test. I employed the more in- 

 tense light of the sun, which was varied in two stages, from 

 0-4 S to S. The temperature was carried through a cycle 

 of ten stages, from 22 C. to 35 C, with each of these two 

 intensities of light. I give first a table of detailed values 

 of activity under each variation of temperature : (1) under 

 0-4 S, and (2) under S. The curves which show these rela- 

 tions are of extreme interest. The stronger intensity of 

 light S is two and a half times greater than the lower 

 intensity 0-48. The Law of Product is verified by the fact 

 that the partial effect of the light-factor caused the same 



