NEW STA WHE. 72 
‘grate continues in the fame pofition, will throw up as ufual 
a body of thick fmoke. But every one accuftomed to coal 
fires in common grates, muft have obferved that pieces of 
frefh coal ftuck in below among the red coals have their 
fmoke fo heated as that it becomes flame as falt as it is 
produced, which flame rifes among the coa!s and enlivens 
the appearance of the fire. Here then is the ufe of this 
fwivel grate. By a pufh with your tongs or poker, you 
turn it on its pin till it faces the back of the chimney, then 
turn it over on its axis gently till it again faces the room, 
whereby all the frefh coals will be found under the live 
coals, and the greater part of the fmoke arifing from the 
freth coals will in its pafflage through the live ones be heat- 
ed fo as to be converted into flame: Whence you have 
much more heat from them, and your red coals are longer 
preferved from confuming. I conceive this conftruction, 
though not fo complete a confumer of all the fmoke as the 
vafe, yet to be fitter for common ufe, and very advanta- 
geous. It gives tooa full fight of the fire, always a plea- 
fing obje&t, which we have not in the other. It may with 
a touch be turned more or lefs from any one of the com- 
pany that defires to have lefs of its heat, or prefented full 
to one juft come out of thecold. And fupported ina ho- 
rizontal pofition, a tea-kettle may be boiled on it. 
The author’s defcription of his Pennfylvania fire-place, 
firft publifhed in 1744, having fallen into the hands of 
workmen in Europe, who did not, it feems, well compre- 
hend the principles of that machine, it was much dif- 
figured in their imitations of it; and one of its main in- 
tentions, that of admitting a fufficient quantity of frefh 
air warmed in entering through the air-box, nearly de- 
feated, by a pretended improvement, in leflening its paf- 
fages to make more room for coals in a grate. On pre- 
tence of fuch improvements, they obtained patents for the 
invention, and for a while made great profit by the fale, 
till the public became fenfible of that defe@t, in the ex- 
K pected 
