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:
Cowper's aversion from tobacco could not have been very strong, for he encouraged his friend to smoke in the famous Summer House at Olney, which was the poet's outdoor study. Bull smoked Orinoco tobacco, which he carried in one of the tobacco-boxes, which in those days were much more commonly used than pouches, and this box on one occasion he accidentally left behind him at Olney. Cowper returned it to him with the well-known rhymed epistle dated June 22, 1782, and beginning:

If reading verse be your delight,
'Tis mine as much, or more, to write;
But what we would, so weak is man,
Lies oft remote from what we can.