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. 
D{RECTION IN MOVEMENT OF MEAN MONTHLY PRODUCTION. 
Station Jan. | Feb.| Mar. Apr.| May June} July | Aug.| Sept.} Oct. | Nov. | Dec. 
ae eee eee ee lesen le lee ie 
\E as als asd al aS als al als a5 als al 5 a. 
pm PAA bPAHnA DA HAHA BA pA BA HAD 
Miinois River... .....||0 12es|| aime WLea|es Glue 2issisica alg su.2Uan al/a2 
Spoon River... ...... teva heal aheahie ol 4 1 eee) [SC ead alec) a ol O} 1.21 
Quiver Lake................. 2.1) 0....41 1...3 0.4! 2 | On|) 4/3 2 3 4 | chee [Rb pa 
Dogfish Lake ......... 14 al eet 2! 0 2 2 ol Zewl\ite sable ed deen Tr | eel (0e 2 
Flag Lake... Seve Al Tet (0 | 0.....2| 0 | DO | O)eee2 || ele 1| Oe | 2220)! 2 
Thompson’s Lake Pes aoe espe | toes need lic 3! pt WER RAO) PRS eh Aan tee ocean lf ere er | 
Phelps Lake _ 1,.,..0; 0.....2} 1....2) 0.....3, 1 : 3.....0) 1.2) 1.2) L....0 1.1) 0 ...2) 1....0 
Toten u 3) 9.13 6.16] 1 v 8 1115 _a|14....9]12.. 12.12 1213. 7|13....8]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 ofthe backwaters, 
though on the whole the instances of rising and falling produc- 
tion are equal in number. In October and November produc- 
