507 



duction to a slight degree in the localities examined and in the 

 region as a whole. The following table exhibits the instances 

 of upward and downward movement in the monthly means for 

 each locality for each month of the year. 



DIRECTION IN MOVEMENT OF MEAN MONTHLY PRODUCTION. 



Station 



Illinois River 



Spoon River 



Quiver Lake 



Dog-fish Lake 



Flag- Lake 



Thompson's u,ake 

 Phelps Lake 



Jan. Feb. 



o o. o 

 Q D Q 



3 



1... 1 

 3.-..1 



1 



1 . .0 

 2 1 



.0, 2. 

 2.. 

 0. 

 1. 

 1. 

 3 



Total 11....3I 9... 13 



Mar. Apr. 



a ' a 



"f £ 



o P. o P< 



p £ a D 



..2 0.. 



2 1 1 



2 

 1 



i 



. .2 



..3 0.. 



J 



Mav June 



July 



a a 



& Ss 



D< o Pi O P. o 

 ID P P P UP |D 



.! 1_ 



Aug 



1... 2 3..... 2 2 



Sept 



Oct. Nov. 



b o< o P. o Pi 



Q Pfl &R (D 



2, 2..-. 2.. 1 



2i 3 



. .21 2.. . 



I 

 1 3 4 



1...2, 3.....0 



.16! 1...19 8 .11 IS.. ..7 



i 



3 .2 4.... 3 3... 2 ! 3 



1... 1. . 



..1 1 1 



2| 2 ...3 

 . 1 

 ..1 



4.1 

 1.....1I 1 ..1 



1 1 . ..1 



2 3 3 1 



2| 1 1 . ..1 



9 12... 12 12 .12 13.. .7 13 



3 2 



1.. 1 



2 



3 1 



.. 2 



Dec. 



o P. 

 P P 



10.. .11 



This table, combined with the plottings of the averages of 

 the monthly means at each station, shown in Fig. E (p. 508), 

 indicates the following course in production which predominates 

 in our records. Production falls in January, begins to rise in 

 February, continues to increase in March, but only to a slight 

 extent though more generally. In April the increase is prac- 

 tically universal and more extensive than in any other month 

 of the year. In May the increase continues in the majority of 

 instances (11 out of 19), and more frequently (63 per cent.) in the 

 backwaters than in tributaries (50 per cent.). In either June 

 or July there is a decline to a lower level of production in all 

 localities. There is, however, considerable diversity in this 

 matter in the several years and localities (partially as a result 

 of imperfect records). This appears in the ratios of downward 

 and upward movement in June (15 to 7) and in July (14 to 9). 

 In the months of August and September there is a tendency 

 towards a higher level of production in some of the backwaters, 

 though on the whole the instances of rising and falling produc- 

 tion are equal in number. In October and November produc- 



