INFLUENCE OF THE FOEESTS ON NAVIGATION. 



27 



millions of dollars. Table 13 shows the freight tonnage in 1905 and 

 the cost of improvements by the United States Government, together 

 with other facts. 



Table 13. — Rivers which have their sources in the White Mountains, showing, for each 

 river, distance navigable, annual tonnage according to latest statistics, total appro- 

 priations 1790 to 1907, average expenditure of government money per mile, tonnage of 

 commerce per mile according to latest statistics, and tonnage (1905) for each dollar spent 

 by the Government, between 1790 and 1907, for improvements. 



Name of river. 



Miles of 

 naviga- 

 ble 

 water. 



Tons of 



freight 



carried in 



1905. 



Appropria- 

 tions by the 

 Government 

 from 1790 

 to 1907 for 

 improve- 

 ments. 



Total cost 

 of improve- 

 ments per 



mile of 

 navigable 



water. 



Average 

 tonnage 

 per mile of 

 navigable 

 water in 

 1905. 



Average 

 tonnage on 

 the river in 



1905 for 

 each dollar 

 spent by 

 the Gov- 

 ernment 



for 

 improve- 

 ments 

 from 1790 

 to 1907. 





44 



30 



5 



m 



50 



400,735 



$667, 445. 71 



S15, 169. 22 



9, 107. 61 



0.6004 







Saco 



48, 537 



88,324 



673, 383 



346,775.00 1 69,355.00 

 825,366.72 47,162.09 

 737,510.69 I 14,750.21 



9,707.50 

 5, 047. 07 

 13, 467. 66 



.1390 





.1070 





.9170 







Total 



146Jr 



1,210,979 2,577,098.12 | 17,591.11 









8,266.07 



.4699 





i ! 





The influence of forest removal upon navigation is marked in 

 three ways — it increases the floods, it makes the low-water stages 

 lower and prolongs them, and it deposits large quantities of silt in 

 those parts of the streams where obstruction is most objectionable.^ 



George F. Swain, professor of civil engineering in the Massachusetts 

 Institute of Technology, says of the first of these influences : 



Some of the effects on the streams of wholesale destruction of timber are perfectly 

 well known. It is certain enough that they are subject to more sudden fluctuations 

 and are less sustained in droughts than before the country was cleared. These results 

 are matters of common observation among men whose memories reach back over 

 fifty, forty, or even twenty years; it is a universal complaint in New England that 

 the mill streams are less reliable, except of course where artificially reservoired, 

 than they were that length of time ago, and this is due both to the clearing of land 

 and the drainage of swamps. The principal freshets in the region under discussion 

 are caused by the melting of snow in the spring, and while the effect of forests is, by 

 shading the ground, to prevent this going on too rapidly, so on the other hand their 

 destruction lays the surface open to the direct action of the sun and gives a good 

 opportunity for a quick melting away of the snow. The record of the heights of 

 freshets in the Connecticut for thirty-five years back shows that in this stream, whether 

 we have regard to the highest freshets of the year or to the highest occurring during 

 the first five months, which latter may be supposed to have connection with the 

 melting of the snow, there has been a considerable increase in the average heights 

 reached. 



a Volume XIV, Tenth Census. 



[Cir. 168J 



