[ 5 6 3 
engine, which keeps a continual blaff whilff the en- 
gine works ; the ffrength of which is increafed or 
dimini fhed, by adding or taking off the weights on 
the bellows. 
The effedt produced, according to the befl ob- 
fervations I could make, was, firft, a very vifible 
alteration for the better in the working of the engine. 
When the fire was ffirred, as. it muft be every time 
fuel is added, the fteam generally became too fierce, 
which occafioned great irregularity, and fometimes, 
if not watched, great damage to the engine ; and 
when the fire abated, the ffroke became immediately 
much fhorter, or flopped intirely, if fuel was not foon 
added : whereas, by blowing air thus thro’ the water, 
it keeps, with any moderate care, an equal ffroke 
to its full length, from the beginning to the end ; 
and by that means difcharges a confiderably greater 
quantity of water. A proof of which was very evi- 
dent, tho’ I could not afcertain the exadt quantity : 
for the engine, before this improvement, fupplied 
but two main- pipes at once* which conveyed the 
water to the houfes ferved by them ; but fince could 
not take off the quantity of water thrown up, part 
of which was obliged to be difcharged into a third 
main. 
As to the quantity of fuel, that may be faved by 
this method, it is not eafy to determine from any 
experiment on this engine, the boiler and fire-place 
of which is made very different from all others, and 
the quantity of fuel already thereby greatly lefiened. 
The fire-place, which may be faid to be within the 
boiler, and is but barely large enough to contain a 
quantity of the roundeft and ffrongeft burning coals 
fuflicient 
