Smoke, caused by smoldering: leaves, dried dung, or decayed wood, is a well known way to pacify and calm bees. It is used by man to help us gather honey and wax, check hives, and is still in modern use as the simplest and most effective way to handle bees, and their hives.
It affects the bees by making them engorge themselves with honey - which can be regarded as them taking on a full load, ready to flee a fire. This is helpful because a full bee is much less likely to sting than a hungry empty bee.
Whatever is burnt in a smoker, or chafing dish, should produce a thick cool smoke (preferably white, for some reason) with little deposit. For many centuries the hives where smoked only once, when the honey and wax was collected, using smoke that contained substances which narcotized (and at higher concentrations killed) the bees. These included tobacco, puffball, and in one example brimstone.
Our earliest example of a smoker is Egyptian, and dates 2400 BC. There is a picture of a worker holding a dish working an open hive. The dish has smoke vapor coming from it. Later in Rome, Virgil directs beekeepers to, "in your hand hold forth searching smoke" (Georgics IV.228), whilst his contemporary Columella goes onto describe a smoker as a pot with holes.
Today smokers are columns which are stuffed with leaves. Bellows are attached, so the beekeeper may produce a thick smoldering smoke upon his (or Her) bees.
Crane, Eva. 1983. "The Archaeology of beekeeping", Duckworth. London. ISBN 0 7156 1681 1
Crane, Eva. (unknown). "history of protective measures against stinging by bees" (unknown) - I have a 3rd generation photocopy - sorry. | 
