580 



SCIENCE. 



[N. S. Vol. III. No. 



reliable and long-contiuued observations of 

 discharge been made. Your Association 

 meets this year upon the banks of the Con- 

 necticut river, upon whose upper drainage 

 area the clearing away of the forests has 

 been for many years, and still is, progressing. 

 At two points upon this river, Hartford and 

 Holyoke, an unusual number of continuous 

 observations of flow have been made, and it 

 has seemed to me desirable to examine 

 them and see whether they reveal any 

 changes in the character of the flow which 

 could be ascribed to the cutting of the 

 forests. 



At Hartford the tributary area is about 

 10,200 square miles, and for a period of 

 over fifty years records are available of the 

 maximum freshet height of each year. Fur- 

 ther, observations to determine the daily 

 rate of discharge were begun in 1871 by 

 General Theodore G. Ellis, and were con- 

 tinued without interruption until 1886, al- 

 though for 1882 and 1883 the figures are not 

 at hand. There was thus obtained a record 

 having few parallels in this country, and it 

 is deeply to be regretted that the United 

 States engineers should have permitted it to 

 be discontinued, as was done in 1886. At 

 Holyoke, where the drainage area is about 

 8,000 square miles, the Holyoke Water 

 Power Company has maintained since 1880 

 a daily record of the discharge of the river 

 past that point, which record is still contin- 

 ued and is on the whole the most valuable 

 that now exists regarding the discharge of 

 this stream. 



The effect of forest cutting within the 

 past twenty-five years should, of course, be 

 most evident in the upper river, since it is 

 near the head waters that operations have 

 been mainly conducted in that period. It 

 will be of interest, however, to study the 

 only records that are available — those for 

 the lower river — and see if we can there 

 detect any marked change in the nature of 

 its flow. 



The theory as to the effect of forests is, 

 that by shading the ground they tend to 

 prolong the melting of snow in the spring, 

 and thus to prevent excessive freshets, as 

 well as to maintain the naturally decreas- 

 ing flow of late spring and early summer. 

 Further, by reducing the evaporation from 

 the ground, by obstructing the free flow of 

 surface water after rains, as well as by con- 

 serving the snows, they tend to maintain a 

 large volume of ground water, which, issu- 

 ing in visible springs or in invisible see- 

 page, must of course be the reliance of all 

 streams in dry weather. The effect of ex- 

 tensive forest-cutting might, therefore, be 

 expected to be an increase in the number, 

 suddenness, and height of oscillations, and 

 on the other hand a more speedy falling 

 away in summer and a lower range of dry 

 weather flow. To reveal clearly any per- 

 manent change that may have taken place 

 in the Connecticut river it seems to me that 

 we should have continuous records of flow 

 for a longer period than they are yet avail- 

 able, and that for successive groups of 

 years curves should be constructed, by 

 averaging for each group the lowest daily 

 discharge, the second lowest, and so on, ir- 

 respective of calendar order. The distribu- 

 tion of the flow would thus be shown in a 

 manner warranting the drawing of positive 

 conclusions. Because the labor involved in 

 such a treatment is large, and because the 

 records cover so short periods as hardly to 

 warrant it, I have limited mj^self to an ex- 

 amination of freshet heights and of low- 

 stage flow. 



The heights above low water datum to 

 which the river has risen in freshets at 

 Hartford since 1840 are as follows : 



1841 26.3 



1843 27.2 



Dec. 1844 19.5 



Apr. 1845 19.0 



Mar. 1846 18.8 



Apr. 1847 21.0 



Jau. 1848 1.5.5 



Nov. 1849 17.5 



Apr. 1869 26.7 



" 1870 25.3 



May 1871 18.7 



Apr. 1872 19.7 



" 1873 21.0 



Jan. 1874 23.9 



Apr. 1875 18.7 



" 1876 21.8 



