l60 CHAP. XIX. THE DAILY VARIATION IN ACTIVITY 



were now four bubbles, represented by as many spacings, 

 in the course of five minutes. The activity increased 



Fig. 44. Automatic Records of successive Bubblings for five 



minutes during different periods of the Day- 

 Note the slow rate at 7.30 a.m. and 4.30 p.m., and the quick 



rate at midday. 



rapidly : by 8 a.m. the rate had risen one and a half 

 times, there being now 6 spacings in the record. At 

 8.30 a.m. the activity was enhanced to about three times 



