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:
A famous crony of Parr's, the learned Porson, was another devotee of tobacco. In November 1789 Parr wrote to Dr. Burney: "The books may be consulted, and Porson shall do it, and he will do it. I know his price when he bargains with me; two bottles instead of one, six pipes instead of two, burgundy instead of claret, liberty to sit till five in the morning instead of sneaking into bed at one: these are his terms:" and these few lines, it may be added, give a graphic picture of Porson. According to Maltby, Porson once remarked that when smoking began to go out of fashion, learning began to go out of fashion also—which shows what nonsense a learned man could talk.