Take, for instance, the art of making bread, which was probably practised by the earlier races in some such manner as that represented in the figure. , wherein is depicted the process employed by certain savage tribes at the present day. Rude as the process is—and it consist only in spreading the paste, made of flour and water, on a series of flat stones which have been heated in a fire—its employment betoken the knowledge of a certain number of the facts of nature. It required the experience of perhaps many ages to impart the knowledge of other fads by which the originally .rude process became improved. This progress of an art, from its rudest to its more advanced state, doe not necessarily imply an advance in science.