594 Mr. mann’s Treatife 
5thly, Wherever there is a confluence of rivers or ca- 
nals, the angle of their junction rauft be made as acute 
as poffible, or elfe the word: of confequences will .arife 
from the corrofion of their refpective ftreams; what 
they carry off from the fldes will be thrown into irregu- 
lar banks in the bottom of the bed. This acute angle of 
junction may always be procured by taking the direction 
at fome diftance from the point of confluence. 
6thly, Wherever the fldes or banks of a river are lia- 
ble to a more particular corrofion, either from the con- 
fluence of ftreams, or from irremediable windings and 
turns in the channel, they muft be fecured againft it as 
much as poffible by weirs: for this corrofion not only 
deftroys the banks, and alters by degrees the courfe of 
the river, but alfo fills up the bed, and thereby produces 
all the bad effects we have fpoken of above in N° 33. 
34. <kc. 
7thly, But the principal and greateft attention in dig- 
ging the beds of rivers and canals muft be had to the 
quantity and form of their declivity . This muft be done 
uniformly throughout their whole extent, or fb much of 
it as is neceflary for the purpofes in hand, according to 
the principles laid down above (in N° 29 and 30.) Con- 
formable thereto, the depths of their beds, and of the 
floors of their fluices, at the mouths whereby they dif- 
charge 
