By the consumption of wealth is meant the using of wealth in the gratification of human wants; the carrying out of the purpose for which the wealth was produced. Consumption does not involve primarily or even necessarily the destruction of the thing which has been produced. It is true indeed that such destruction is usually attendant upon consumption but it is not essential to it. The essence of the consumption is the utilization of the thing, the gratification of the desire. Thus, coal in being consumed for the purpose of furnishing heat changes its form and is no longer coal; a painting, on the other hand, is consumed in the economic sense not by having its form changed but by being placed upon the wall and being seen and enjoyed. Under the head of consumption we study wants, and their satisfactions.