Two processes must be carried out in order to yield any scientific result: facts must be patiently accumulated, and the mind must set its reasoning powers to work on them. It was in the first of these that the Greeks were wanting. They did not realize the need of endless patience in learning the details of Nature's way of working. They wished to take in all of Nature with one tremendous sweep of thought. They did a little investigating and a great deal of reasoning. Occasionally, however, we find an instance of inquiry into the cause of more definite and limited phenomena, which seems much more to suggest the true spirit of physical inquiry. We have one recorded by Herodotus, which is the more remarkable from being so nearly alone. It is in reference to the fact which he had observed about the flooding of the Nile--that it was flooded for one hundred days, beginning with the summer solstice; and that from that time it diminished, and was during the winter months very low. He tells us that he made pressing inquiries about the cause of it from many of the Egyptians, but that he found no satisfaction, and apparently little interest in the matter. Three different theories on the subject that had been propounded by the Greeks he examines in detail and confutes; and finally he states a theory of his own. And yet even in this instance of scientific inquiry he commits the usual fault of the Greeks--he does not pursue far enough the investigation of the facts of the case, and the absence of the facts he tries to make up for by exhaustive arguments on words used in describing the phenomena.