346 Dr. percival’s Account of a 
cent work on this fubjeCt, of which he has favoured 
me with a copy, has not even mentioned it. 
But thefe refervoirs may he applied to a purpofe 
Hill more fubfervient to public utility than that above 
defcribed. josiah birch, Efq. a gentleman who carries 
on an extenfive manufactory, and bleaches his own yarn, 
about fix months ago, was induced, by a happy turn of 
thought, to try whether the dung-hill water might not 
be converted into pot-aflies. He accordingly evaporated 
a large quantity of it, apd burnt the rejiduum in an oven ; 
the product of which fo perfectly anfwered his expecta- 
tions, that he has ever fince continued to prepare thefe 
a fhes, and to employ them in the operations of bucking. 
A ftranger to that narrownefs of fpirit which feeks the 
concealment of a lucrative difcovery, he is defirous that 
it fiiould be communicated to the Royal Society, and has 
furnifhed me with the following account, together with 
the plan annexed. ^ 
“ The quantity of muck water ufed was twenty-four 
“ wine pipes full, which employed a man and two 
<£ horfes two days, to cart it from the pump to the pan 
“ wherein it was boiled ; but this expence I fhall now 
“ fave, as I fhall lay a fough of brick, which will convey 
“ it from the pump to the boiler. The coals ufed to 
“ boil and burn it were one hundred and twenty bafkets, 
1 “ and 
