( 7i4 ) 
lead are applyM in a fenfe fomewbat different from their 
common Acceptation; for which rea on he begins his 
Work with a Sett of Definitions. 
^^tta mortua, or a dead Water is that whofe Surface 
being every where equally diflant from the 
viuWf no part of it can defeend any lower, without for- 
cing fome other upward, and confeqw-iitly the Whole 
is without Motion. 
viva, or a running Water is that which is put 
into motion by the Prefiure of the Incimibcnt Water, 
and whofe Motion is oppofed by no other Water lying 
in its way. 
The motion of a running Water is call’d Motus fim* 
flex, or the fimple Motion. 
If a running Water m )Vtng over the Surface of a 
dead Water, do, by its Prefiure, communicate part of 
its Motion to the dead Water ; the compound Motion 
with which the whole Body of the Water flows, is 
called Motus mixtus, or the mixt Motion. 
If a Water at different Depths from the Surface run 
with different Velocities, thewr^w is that, which 
being the fame at all Depths, will difeharge the fame 
Quantity of Water. 
Next follows a ftiort Hiftory of the Original, and 
Progrefs of the Dodrine of running W'aters, the Inven- 
tion of which our Author juftly afierts to the Learned 
Cafiellus, and defends him againft Fabretti, who has 
maintain’d that Cajlelluss fundamental Propoficion of 
the Quantity difeharged being cateris faribm in pro- 
portion to the Velocity, was known, and publickly 
taken notice of before him by Frontinus, 
The Author allows CafleUus to have been miflaken 
in determining the Velocity of Water running out at 
the bottom of a Veflel, he having aflerted that Velo- 
city to be as tlie Depth of ihe Water. 
Three 
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