FISHERIES, GAME AND FORESTS. 513 



evaporation 2 1. 8 1 inches. In 1895, the rainfall was 29.84 inches, the run-off 4.90 

 inches, and the evaporation 24.94 inches. For the year 1896 the data, although at 

 hand, has not yet been reduced. As we have already seen, the Upper Genesee River 

 in Western New York gave in 1895, with a rainfall of 31 inches, a run-off of only 6.67 

 inches. On the Muskingum River for that year, with a rainfall of 29.84 inches, the 

 run-off was only 4.90 inches. The evaporation of the Genesee River, in 1895, was 

 24.33 inches, and of the Muskingum River, 24.94 inches. The year 1895 was 

 undoubtedly the year of about minimum rainfall for both these drainage areas; hence 

 we may draw the tentative conclusion that on deforested areas for the belt of 

 country included by these two streams, the evaporation will be for the year of 

 minimum rainfall somewhere in the vicinity of 24 to 25 inches. After this element is 

 satisfied, whatever surplus there may be will appear as run-off in streams. This con- 

 clusion, it must be remembered, applies only to these areas while in their present 

 deforested state. The mean temperature of the Genesee area is about 43" F.,and that 

 of the Muskingum from 48" to 50° F. The incomplete state of the tabulations to 

 which I have referred render it impossible to give the final figures at this time. The 

 drainage area of the Muskingum River is about 6,000 square miles. A considerable 

 portion of this area is of a clayey character, the surface formation being that known 

 to the State Geologists as bowlder clay. In many places it exists to a great depth 

 and is stated to have radically changed the preglacial courses of the streams. It has 

 little porosity and water sinks into it with difficulty. Springs are rare, and by the 

 middle of July many of the streams dry up and so remain until late into the fall. A 

 considerable portion of the Muski'igum drainage area has been thoroughly under- 

 drained by the tile drainage. 



As another stream we may refer to the Des Plaines River in Illinois, of which 

 more or less complete gaugings ha\e been kept, from 1886 to 1897, inclusive. In 

 1889, the mean rainfall of the Des Plaines drainage area, as deduced by taking the 

 means of a large number of stations in Illinois and Wisconsin, was 34.99 inches; the 

 run-off, 5.06 inches; the evaporation, 29.93 inches. In 1893, the rainfall was 26.96 

 inches, the run-off 10.14 inches, and the evaporation 16.82 inches. In 1894, the 

 rainfall was 27.94 inches, the run-off, 7.70 inches, the evaporation, 20.24 inches. In 

 1896, the rainfall was 39.08 inches, the run-off 6.69 inches, and the evaporation 

 32.39 inches. As a tentative conclusion we may say, then, that with full rainfall the 

 Des Plaines River drainage area will show an evaporation in its present deforested 

 state of about 30 inches per year. With deficient rainfall, the evaporation will be less 

 in some proportion to the deficiency. 



The reservoirs on the Upper Mississippi may also be referred to. Taking the 

 records as kept at the Pokegama dam, where the total area of contributing watershed 

 33 



