on Rivers and Canals* 613 
to the infinite wifdom of the Author of Nature, in the 
original difpofition of things. 
49- We have feeri above (N° 1 8. 27. 28.) that the In- 
creafe of a river or canal by the new waters which it re- 
ceives, is urtiv erf ally in an inverfe ratio of the new v\ t lo- 
ci ty which is acquired therefrom . If this velocity is greater, 
the increafe of the fedtion of the new Dream will be lefs 
in proportion, and vice verfd. It follows from hence, 
that it is poflible for one river or open canal to fall into 
another river or open canal of equal magnitude with it- 
felf, and yet the feftion of the current in the common 
bed after their confluence fhall be no greater than it 
was in each of them before their junction. It is certain 
that this will be the cafe as often as the confluence of the 
two augments the velocity of the common current in the fame 
proportion with the increafe of the volume of waters', both 
the greater rapidity of the current, and the greater volume 
of water in the bed after the junction, ferving to deepen 
it in proportion to its breadth, will contribute towards the 
above effeft . Another caufe will likewife add thereto; 
to wit, that inftead of the refiftance from the attra£lion, 
fridlion, and other obftacles, in two beds, which give two 
bottoms and four .tides, there are, after the confluence, 
only thofe of one bed, of one bottom and two tides. 
Moreover, the center of the feftion in the common bed 
Vol. LXIX. 4 L 
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