"Upon Inquiry from knowing Persons, I find that Norway or Swedish Tar, which is dark, thick and clear... is accounted the best for the general Uses... But that the Tar which is made of the Tops of -Trees... having lain long dead... after having either fallen... or being killed by the draining off their Sap... (These Tops are commonly called Light-wood, the poorer People making use of them instead of Candles:) This Tar being burned in a very strong Fire of such dry Wood, is of a very caustick, corroding Nature, so as to be hurtful to Ropes, &c. for which reason it is not used in the Royal Navy. But the American Tar, which is made of green Fir-Trees, with a less degree of Fire, is esteemed good, and is called green Tar..."
January 1, 1970
https://en.wikiquote.org/wiki/Stephen_Hales