( «4 ) 
Weight of the Mercur'j being balanc’d, is no Hindrance, 
whether you work with a Tingle or a double Barrel- 
There remains only then the Hindrance by loTs of 
time in the Beginning of any Stroke : But I have 
Ihew’d that to be but tv part of the Broke. I have 
found that the beft Engines now in ufe generally 
lole near -f of the Water that they ought to give, 
according to their Number of Strokes. And Mr. 
Hent'j Beighton^ an ingenious Member of this Socie- 
ty, having a great many times meafur’d the Water 
that is rais’d by Engines in Mines, found that fome 
Engines loft and none ever loft lefs than t of 
what they ought to give according to the Number 
of the Strokes in their Pumps, whatever auxiliary 
Powers they were mov’d with. 
There is indeed another Objedion, but fcarce worth 
notice, which is, that fome Particles of Mercury will 
mix with the W^ater that is rais’d, and make it un- 
wholefbme; but no body that confiders Specifick 
Gravity, will imagine any fuch thing. However, to 
fatisfie thofe that might ftill apprehend it, it is to be 
obferv’d, that none of the Water that is rais’d comes 
near the Mercury; For in the Cylinder C, and part 
of the Elbow B, (^Fig. 5 .) there is always above the 
Mercury a certain C^antity of Water that tifes and 
falls with the Barrel, and never goes into the forcing 
Pipe. The fame happens alfo in the Machine of 
Fig. 6. for the Water having once run into the Cy- 
linder C, all that is rais’d afterwards, comes thro’ the 
forcing Valve without coming down to the Mer- 
cury, 
Provided Care be taken to make the Barrel with 
its Plug tight, 1 don’t fee that this Machine will 
want Repair in a long time, except fome of the aux- 
iliary Powers be out of order, which do not relate to 
this 
