172 CHAP. XX. EFFICIENCY OF DIFFERENT COLOURS 



sensitiveness of the specimen had not undergone any change 

 during the whole period of the experiment. It will be noted 

 that under sunlight the maximum flotation was attained 

 in the course of 1 minute, the fall being practically 

 instantaneous on the bursting of the bubble. Under red 

 light the rate of ascent was, however, comparatively slow, 

 and the ascensional movement was completed in the course 

 of 3-5 minutes. A striking difference is observed in the 

 curve under blue light. The bubbles were formed at a very 

 slow rate, so that the slope of the response-curve is much 

 flatter than that under red light ; the movement of flotation 

 was completed in the course of 7-5 minutes. The last 

 record under sunlight is practically the same as the first, 

 proving that the sensibility had remained constant. 



The relative ineffectiveness of blue light in comparison 

 with red is thus demonstrated by two independent methods, 

 which show different periods of flotation and the charac- 

 teristic differences in the response-record, the response of 

 the relatively ineffective blue light being characterised by 

 a flatter curve. 



The periods of flotation in two different specimens were 

 as in the following table : 



Table XXIV. — Showing Periods of Flotation under Different 



Lights 



Specimen I. Specimen II. 



Period of flotation under blue light . 455 399 



„ red „ 224; 186;; 



sunlight . 55 53 



The ratio of activities in the first case is : 



B:R:S: : 1 : 2:8-2 (2) 



In the second case it is : 



B: R: S: : 1 :2-i :7-6 . . . • (3) 



