57^ 
/ 
4 
turpentine kind, yet as it has been found that fome fpecies produce 
theie different articles of the Materia Medica in greater purity, or in 
more abundance than others : we have accordingly affigned to each, 
the refpective article which it bell fupplies. This tree not only fur- 
nifhes mofl abundantly the Pix liquida, or Tar, but alfo from it 
may be obtained the common turpentine, and the white and yellow 
refins. ' , 
The manner in which the Tar is procured is by cutting the tree 
into pieces, which are inclofed in a large oven conftrudted for the 
purpofe, with a channel at the bottom. A fufficient degree of heat is 
then applied, by which the tar is forced out of the wood, and runs 
off by the opening at the bottom : a procefs termed dillillatio per 
defcenfum. 
Tar, which is well known from its ©economical ufes, is properly 
an empyreumatic oil of turpentine, and has been much ufed as a 
medicine both internally and externally. Tar water, * or water im- 
pregnated with the more folubile parts of tar, was fometime ago a 
very popular remedy in various obftinate diforders, both acute and 
chronic; efpecially in fmall-pox, fcurvy, ulcers, nftulas, rheumatifm, 
afthma, coughs, cutaneous complaints, &c. and though its medicinal 
efficacy was greatly exaggerated by the publications of Bifhop Berkeley 
\ 
Prior, and others, yet Dr. Cullen acknowledges that he experienced 
this preparation in feveral cafes to be a valuable medicine, and that 
ppeared to ftrengthen the tone of the llomach, to excite appetite, 
promote digeftion, and to cure all fymptoms of dyfpepfia. At the 
fame time it manifeftly promotes the excretions, particularly that of 
urine; and the fame may be prefumed to happen in that of others. 
From all thefe operations it will be obvious, that in many diforders 
of the fyftem this medicine may be highly ufeful." a 
* The proportions that have been commonly employed, are two pounds of tar to a 
gallon of water ; which are to be well ftirred together, then fuffered to fettle for two 
days, and the clear liquor poured off for ufe. From a pint to a quart, according to 
circumftances, may be taken in the courfe of twenty-four hours. Dr. Cullen thinks 
with Mr. Reid, that the acid principle gives the virtue to tar water ; and hence the 
Bifhop of Cioyne properly preferred the Norway tar to that of New England, as the 
more acid 
Mat, Med. vol, iu p. 334* 
An 
