One evening, in February, 1898, I left my desk and, stepping to the window, looked out at Polaris and the circumpolar region of the sky, with a newly awakened and eager interest. For thirteen years I had been studying and collecting material with the hope of obtaining some understanding of the calendar, religion and cosmogony of the ancient Mexicans, but had hitherto purposely refrained from formulating or expressing any conclusions on the latter subjects having felt unable to extract a clear and satisfactory understanding of the native beliefs from the chaotic mass of accumulated data under which they lay like the ruin of an ancient temple. Though frequently discouraged, I had, however, never ceased to pursue my research and to note carefully the slightest indication or suggestion which might prove of ultimate value. Becoming utterly absorbed in the collection of such notes, I found no time to publish anything during the past four years, though realizing, with regret, that those interested in my work might be disappointed at my delay in issuing the papers announced, in 1894, as speedily forthcoming. Slowly but steadily, however, I was gaining ground. Various excursions along new lines of research increased my experience and, in crossing and re-crossing the field of ancient Mexico, I frequently had occasion to observe certain familiar landmarks, from a new point of view, and illuminated by rays of fresh light proceeding from recently acquired sources. It was remarkable how often facts, which had seemed so hopelessly complicated, finally appeared to be quite simple and comprehensible. This was noticeably the case with the Aztec deities which, for years, had seemed to me as numberless. After closely studying their respective symbols, attributes and names, during several consecutive months, and subjecting them to a final minute analysis, I found that their number dwindled in a remarkable way and also verified the truth of the statement made by the anonymous author of the Biblioteca Nazionale manuscript which I was editing, that the Mexicans painted one and the same god under a different aspect “with different colours,” according to the various names they gave him in each instance.