TRANS AWE TIONS 
OF Heo wie vi re 
American PHILOsoPHICAL SocleTy, 3. 
N° I. 
4 Letter from Dr. B. FRANKLIN fo Dr. INGENHAUSZ, 
Phyfician to the Emperor, at Vienna. 
Dear Friend, At fea, Auguft 28th, 1785. 
Repo ik one of your letters, a little before I left 
og France, you defire me to give you in writing 
my thoughts upon the conftru€tion and ufe of 
chimneys, a fubje& you had fometimes heard me touch 
upon in converfation.- I embrace willingly this leifure 
afforded by my prefent fituation to comply with your re- 
queft, as it will not only fhow my regard to the defires of 
a friend, but may at the fame time be of fome utility to 
others; the dodtrine of chimneys appearing not to be as 
yet generally well underftood, and miftakes refpeCting 
them being attended with conftant inconvenience, if not 
remedied; and with fruitlefs expence, if the true remedies 
are miftaken. 
Thofe who would be acquainted with this fubject fhould 
begin by confidering on what principle fmoke afcénds in 
any chimney. At firft many are apt to think that fmoke 
is 
