163 



Monthly and Yearly Averages of Readings of River Gage at 

 Havana, 1894-1899. 



(Plane of reference, low water of 1873.) 



Year 



1894. 

 1895. 

 1896. 

 1897. 

 1898. 

 1899. 



Sept. 



4-43 

 3-42 

 4.62 

 2.01 

 4.44 

 2.63 



Oct. 



2.96 



1-93 



6.04 



2. oil 

 4.86 

 2.99' 



Nov, 



2.97 

 2.20 



5 

 2.82 



7-44 

 3- 



Yearly 

 Av. 



463 

 3 61 

 6.98 

 6.90 



8.02 



6.40 



HIGHEST AND LOWEST WATER, RANGE, AND TOTAL MOVEMENT, BY MONTHS, OF RIVER LEVELS FROM 

 GAGE-READINGS AT COPPERAS CREEK, 1894-95, AND AT HAVANA, 1896-1899. 



(Plane of reference, low water of 1873.) 



It is evident that the changes from year to year in the 

 conditions of the river environment are such that they must 

 be taken into consideration in any study of the fluctuations of 

 the plankton, A glance at the general hydrograph (PI. VII.) 

 shows that the years of our plankton work at Havana practi- 

 cally include the extremes of conditions in the river; no two 

 years present the same fluctuations, and both typical and aber- 



