596 Mr. mann’s 'Treatife 
39. I dare boldly affirm, from the certain princi- 
ples of hydrodynamics laid down in this effay, that if the 
above mentioned things (N° 37. 38.) were carried into 
execution in a proper manner ; the velocity of currents 
and the acceleration of motion -of the waters in rivers, 
and in canals when their fluices are open, might be in- 
creafed to any degree that can be required for opening 
their beds, and for preventing inundations during great 
rains or fudden floods : by carrying off more fwiftly the 
great acceffion of water which then takes place. It 
would not be difficult, by tliefe means, to increafe 
the velocity of the current to double and triple what 
it is in rivers and canals, whole beds for a long fpace of 
time have been left to themielves. There is not, per- 
haps, a country on earth but what might be freed from 
inundations by thefe means. But it may be objeited, that 
if all I have advifed was put in execution, even in the 
flatted: countries, the currents of rivers (for canals fliut up 
with fluices are here out of the queftion) would become 
incommodious, if not unfit, for navigation, efpecially 
againft their ftreams. This objection would be of weight 
if it was not evident that the various means which I have 
pointed out may be executed in whole or in part, to a 
certain degree, and no farther than neceffary for the pur- 
pofe# required. But, as it is certain that a ftrong and 
regular 
