But above and beyond this we have to regard Mexican sun-worship from an entirely different point of view. There is abundant evidence that the hunting tribes of the northern steppes, the Chichimec immigrants, possessed a primitive sun-worship of their own. It may be, indeed, that it was from this that the worship of Tonatiuh sprang, and not from the consideration of calendric science; but the criteria we possess regarding this part of the question is at present much too scanty to permit of more precise statement. But if we know that sun-worship obtained among the nomadic tribes of northern Mexico, we are somewhat ignorant of the precise form it took. One thing, however, seems certain, and that is that it was founded on the belief that the sun existed on the blood of animals, preferably deer, and that when these were scarce, on the blood of human beings. If blood-offerings to the sun were to cease, it was thought that the luminary would grow weak, fail, and become extinguished, or else would visit his wrath upon humanity in some such manner as we read of in those myths which recount the recurrent catastrophes of fire, wind, deluge, and earthquakes which the wrathful luminary brought upon mankind. I would, therefore, date the introduction of the solar worship proper into Mexico, and consequently that of human sacrifice, from the period of entry of those northern Chichimec peoples, who, entering the Valley of Mexico at an epoch shortly after the disintegration of the Toltec civilization, adopted an agricultural existence, and finding the supply of wild animals insufficient to meet the requirements of sacrifice, instituted the occasional immolation of human beings. This custom seems, indeed, to have already obtained in the case of the ritual of some of the native gods, for example, Tlaloc and the Earth-mother, and it may be, indeed, that the northern nomads drew the inspiration which prompted them to this evil practice from their more civilized neighbours. But it is even more probable that, as the various Mexican peoples were for the most part of cognate origin and contiguous civilization, the practice of human sacrifice had been common to all of them in a more or less modified form for some generations, and only received an impetus after the Chichimec immigration. Against this view may be quoted the myth which refers the introduction of human sacrifice to a group of Huaxtec earth-goddesses, Tlazolteotl and her sisters. But it seems to me that this Maya people were by no means so prone to the custom, and that in this instance Tlazolteotl has been confounded with some of her Mexican forms. The process by which blood was thought of as being transformed into rain has already been fully described, and it but remains here to indicate that Tonatiuh is, in places, closely identified with the sign atl, water, and is indeed one of the four rulers of the week beginning with the day “one rain,” probably because of the early belief that on