166 
two tubes of the same diameter. It is a good precaution 
always to make them rather too large than too small, for the 
quantity of air admitted into the room may then be regulated 
according to circumstances, by registers for that purpose. 
I do not know that any one has put this method of warm¬ 
ing rooms into complete and successful operation except 
Doctor Franklin in his original Pennsylvania fire-place ; Mr. 
Simeon De Witt in his close marble fire-place ; myself in 
the common open Franklin stove, and Doctor Cooper in his 
cast iron Rumford. It is unaccountable to me, that such a 
plain, obvious and important principle should have been so 
much neglected in practice—A principle too, demonstrated 
by experience to be valuable and practicable, more than 
half a century ago. And above ail it is a matter of aston¬ 
ishment that Count Rumford, in ail his ingenious specula¬ 
tions, should have overlooked one of the most beneficial 
means of warming rooms and neglected entirely the sug¬ 
gestions of the American philosopher. 
I am, sir, respectfully, 
Your most obedient servant, 
B. DE WITT. 
To R. R. Livingston, Esq. President of the Society 
for the Promotion of Useful Arts . 
