With the help of the pottery we can thus gain a more or less reliable conspectus of the development of the late “Neolithic” culture of Egypt. This system of “sequence-dating” was introduced by Prof. Petrie, and is certainly very useful. It must not, however, be pressed too far or be regarded as an iron-bound system, with which all subsequent discoveries must be made to fit in by force. It is not to be supposed that all prehistoric pottery developed its series of types in an absolutely orderly manner without deviations or throws-back. The work of man’s hands is variable and eccentric, and does not develop or evolve in an undeviating course as the work of nature does. It is a mistake, very often made by anthropologists and archæologists, who forget this elementary fact, to assume “curves of development,” and so forth, or semi-savage culture, on absolutely even and regular lines. Human culture has not developed either evenly or regularly, as a matter of fact. Therefore we cannot always be sure that, because the Egyptian black and red pottery does not occur in graves with buff and red, it is for this reason absolutely earlier in date than the latter. Some of the development-sequences may in reality be contemporary with others instead of earlier, and allowance must always be made for aberrations and reversions to earlier types. This caveat having been entered, however, we may provisionally accept Prof. Petrie’s system of sequence-dating as giving the best classification of the prehistoric antiquities according to development. So it may fairly be said that, as far as we know, the black and red pottery (“sequence-date 30--“) is the most ancient Neolithic Egyptian ware known; that the buff and red did not begin to be used till about “sequence-date 45;” that bone and ivory carvings were commonest in the earlier period (“sequence-dates 30-50”); that copper was almost unknown till “sequence-date 50,” and so on. The arbitrary numbers used range from 30 to 80, in order to allow for possible earlier and later additions, which may be rendered necessary by the progress of discovery. The numbers are of course as purely arbitrary and relative as those of the different thermometrical systems, but they afford a convenient system of arrangement. The products of the prehistoric Egyptians are, so to speak, distributed on a conventional plan over a scale numbered from 30 to 80, 30 representing the beginning and 80 the close of the term, so far as its close has as yet been ascertained. It is probable that “sequence-date 80” more or less accurately marks the beginning of the dynastic or historical period.