I «9< I 
Rivers. Eflay on rivers and canals, p. 556, Importance of the fubje£l, ibid. 
Account of authors who have demonftrated the principles laid down by Mr, 
Mann, p. 559, Theory of rivers and canals, p. 563. Definitions, ibid. Laws 
of a&ion in rivers and canals, p. 564. How to find whether the water, in 
a part of a river where the bed is nearly horizontal, flows by the velocity 
acquired in the preceding declivities, or by the compreflion of the upper water 
on the lower in that place, p. 568. How to determine the velocity of each 
particle of water in a regular channel, p. 569. The nature of rivers and 
flowing waters confldered, p. 571. Caufes of the acceleration of motion in rivers,, 
ibid. Caufes of its retardation, p. 372. Principles for calculating the quantity 
of the percuflion of the waters of a river againft an obftacle oppofed to their mo- 
tion, p. 574. Greateft and leaf! velocities of rivers, in what parts to be found, 
p. 576. How to meafure the velocity of the current of a river, or open canal, 
p. 577. Application of the laws of the acceleration and retardation of currents to 
rivers and canals in general, p. 579. How to augment or diminifh the velocity of 
water in rivers, p. 580. The perpendicular compreflion of the upper waters upon 
the lower augments, as all the other caufes of motion in rivers diminifh, p. 581. 
The junction of many ftreams in the fame bed to be attributed to the wifdom of the 
Supreme Being, p. 582. How to dig the bed of a canal fo that the velocity of 
the current fhall be every where equal, p. 583. The depth of a river can only be aug- 
mented to a certain degree, in proportion to its breadth, without hurting the banks 
and weirs made to keep it in, p. 584. Caufes which contribute to fill up the beds 
of rivers, and produce inundations, p. 58 6. Sluices themfelves’ will produce thefe 
accidents, if the floors of their bottoms are not of a depth conformable to the bed of 
the canal, p. 588 — 591. How the principal accidents to which rivers and canals are 
liable may be prevented, p. 590. Great care, in digging the beds of rivers, 
muft be had as to the quantity and form of their declivity, p. 594. Which mull: be 
increafed in equal fpaces, the farther we recede from their mouths, p. 395;. One 
foot perpendicular of declivity to be allowed through ten thoufand feet of horizontal 
extent, ibid. Six machines propofed by Mr. Forfait of Rouen, for removing 
banks formed in navigable canals, p. 598. Other confiderations on the nature of 
rivers and inundations, p. 599. Rivers and canals have their beds raifed, and 
their currents flopped by the fubfiding of mud and heterogeneous matter in different 
places, efpecially juft above their fluices, p. 600. Line of greateft current in a 
river or canal defined, and the changes in the beds of rivers, ariflng from its direc- 
tions from the centers of the fe&ions through which it pafles, enumerated, p. 601.. 
Why inundations are more frequent, confiderable, and do more damage in the in- 
terior parts of a country than towards the mouths of moil rivers, p. 604.. Varia- 
tions in the mouths by which they difcharge their waters into the fea enumerated, 
together with the changes produced by them, p. 605. Effe&s of counter-currents, 
iflands 
