Chemists have distinguished by this name a furnace so constructed that it can always maintain an equal heat, and which shall last a long time without addition of fresh fuel.

The body of the athanor has nothing in it particular, and is constructed like ordinary furnaces. But at one of its sides, or its middle, there is an upright hollow tower, which communicates with the fireplace by one or more sloping openings. This tower ought to have a lid which exactly closes its upper opening.

When the athanor is to be used, as much lighted coal is put in the fire-place as is judged necessary, and the tower is filled to the top with unlighted fuel. The The athanor being much celebrated and used by ancient chemists, it has been particularly described by many authors, and was formerly found in all laboratories. At present this furnace is much less employed, and is even neglected. The reason of this is, that all the ancient chemists were in search of the art of making gold; and being excited by this powerful desire, and confidence of success, they spared no trouble nor expense to accomplish this design. They undertook, without hesitation, operations which required great length of time and unremitting heat. Whereas now, these alluring hopes having vanished, the cultivators of chemistry have no other view than to extend and perfect the theory of this essential part of natural philosophy. This motive, although undoubtedly much nobler than the former, seems, however, to be less powerful over most men. For now, all long and laborious operations whence chemistry might receive great advantages, are neglected, as being tiresome and difficult. There is, in fact, a considerable difference between the hope of explaining a philosophical phenomenon, and that of obtaining an ingot of gold capable of producing many others. Hence the instruments employed in long operations, and particularly the athanor, are now much neglected; and also because the fuel in the tower is apt to stick there or fall down at once in too great quantity. The lamp-furnace, which is a true athanor, may be successfully employed in operations which do not require much heat.