From Chapter 3:
It is pretty clear that not a few of the druggists who sold tobacco were great rascals. Ben Jonson has let us into some of their secrets of adulteration—the treatment of the leaf with oil and the lees of sack, the increase of its weight by other artificial additions to its moisture, washing it in muscadel and grains, keeping it in greased leather and oiled rags buried in gravel under ground, and by like devices. Other writers speak of black spice, galanga, aqua vitæ, Spanish wine, aniseeds and other things as being used for purposes of adulteration.

From Chapter 8:
Notwithstanding the unfashionableness of tobacco, there were still some noteworthy smokers to be found among the clergy. Dr. Sumner, head master of Harrow, who died in 1771, was devoted to his pipe. The greatest of clerical "tobacconists" of late eighteenth century and early nineteenth century date was the once famous Dr. Parr. It was from him that Dr. Sumner learned to smoke. When he and Parr got together Sumner was in the habit of refilling his pipe again and again in such a way as to be unobserved, at the same time begging Parr not to depart till he had finished his pipe, in order that he might detain him, we are told, in the evening as long as possible.