for many Pumps, fince it might every hour raife about 
1800 pounds of Water to the height of 6d Foot: Mean 
while I don^t pretend to have given here the beft propor- 
tion for the bignefs of every part of the Engine ; but it 
fnay be, by altering the Capacity of the Pumps, of tlie 
Pipes, or of the Receptacles, a much more confiderable ef- 
fett might be produced ; but Fie leave this to be lookt af- 
ter by thole that may have occafion for it ; and for my part 
I content my felf having fhewn the truth of what I had at 
firft, though but doubtfully, prapounded : For the River 
&/;^^',v/here it is neareft to yerfatlles, not being above 20000 
Foot diftant, it is eafie to fee that, to fupply this in- 
creafe of diftance,we might lelTen at pleafure the capacity of 
the Receptacles, or increafe the capacity of the Pumps and 
of the Pipes, or caufe the wheel to fpend more time in its 
revolution : \is true the Engine would produce lefs etfccl, 
but upon a great River the number of the En.5ines might 
be multiplied, and vaft quantitys of Water ftiU be railed. 
I flhall therefore, to prevent new difficulties, add only 
this : that as well as in the Receptacles I have a way to 
prevent the overjflowing with Water; lb in the Pumps I 
might alio prevent the ovei'filling with Air, by making 
a Valve that fhould open as loon as the Air in the Pump 
fhouldbe more compreft than the outward Air; So the 
Air getting in through any pores would conftantly be let 
out. 
As for the third objeQiion wherein Mr. /Vr//Vfays that it 
doth not appear how the Water in our Engine may, by Ra- 
refaftion, alcend higher than ^2 Foot. I anfwer that the 
Water doth not at any time alcend higher than from a 
lower Receptacle into the next upper Receptacle, which 
heighth is but 12 Foot; So that it is plain enough that the 
prelfureof the Air may be {iifficieat to drive it up. It is 
indilferent whether it be by Rarefiftioii or other- 
wile that the Water comes into the Receptacle J; it is 
enough that the Water is there, and that the Air preif^s 
upon 
