Naturally, in progressive studies like those of Egyptology and Assyriology, a good many theories and conclusions must be tentative and provisional only. Discovery crowds so quickly on discovery, that the truth of to-day is Often apt to be modified or amplified by the truth of to-morrow. A single fresh fact may throw a wholly new and unexpected light upon the results we have already gained, and cause them to assume a somewhat changed aspect. But this is what must happen in all sciences in which there is a healthy growth, and archaeological science is no exception to the rule.