178 Count Rum ford’s Enquiry concerning the Nature of Heat , 
victuals on the table, and for keeping it hot, the more effectually 
will they answer that purpose. 
Saucepans, and other kitchen utensils, which are very clean 
and bright on the outside, may be kept hot with a smaller fire 
than such as are black and dirty ; but the bottom of a saucepan, 
or boiler, should be blackened, in order that its contents may 
be made to boil quickly, and with a small expence of fuel. 
When kitchen utensils are used over a fire of sea-coal, or of 
wood, there will be no necessity for blackening their bottoms, 
for they will soon be made black by the smoke; but, when 
they are used over a clear fire made with charcoal, it will be 
adviseable to blacken them ; which may be done in a few mo- 
ments, by holding them over a wood or coal fire, or over the 
flame of a lamp, or candle. 
Proposals have often been made for constructing the broad 
and shallow vessels (flats) in which brewers cool their wort, of 
metal ; on a supposition that the process of cooling would go 
on faster in a metallic vessel than in a wooden vessel ; but this 
would not be found to be the case in fact, a metallic surface 
being ill calculated for expediting the emission of calorific 
rays . 
The great thickness of the timber of which brewers flats are 
commonly made, is a circumstance very favourable to a speedy 
cooling of the wort ; for, when the flats are empty, this mass of 
wet wood is much cooled, not only by the cold air which passes 
over it, but also, and more especially, by evaporation; and, 
when the flat is again filled with hot wort, a great part of the 
heat of that liquid is absorbed by the cold wood. 
In all cases where metallic tubes filled with steam are used 
