What that discovery of Law has done for Nature, it is impossible to estimate. As a mere spectacle the universe to-day discloses a beauty so transcendent that he who disciplines himself by scientific work finds it an overwhelming reward simply to behold it. In these Laws one stands face to face with truth, solid and unchangeable. Each single Law is an instrument of scientific research, simple in its adjustments, universal in its application, infallible in its results. And despite the limitations of its sphere on every side Law is still the largest, richest, and surest source of human knowledge. It is not necessary for the present to more than lightly touch on definitions of Natural Law. The Duke of Argyll[3] indicates five senses in which the word is used, but we may content ourselves here by taking it in its most simple and obvious significance. The fundamental conception of Law is an ascertained working sequence or constant order among the Phenomena of Nature. This impression of Law as order it is important to receive in its simplicity, for the idea is often corrupted by having attached to it erroneous views of cause and effect. In its true sense Natural Law predicates nothing of causes. The Laws of Nature are simply statements of the orderly condition of things in Nature, what is found in Nature by a sufficient number of competent observers. What these Laws are in themselves is not agreed. That they have any absolute existence even is far from certain. They are relative to man in his many limitations, and represent for him the constant expression of what he may always expect to find in the world around him. But that they have any causal connection with the things around him is not to be conceived. The Natural Laws originate nothing, sustain nothing; they are merely responsible for uniformity in sustaining what has been originated and what is being sustained. They are modes of operation, therefore, not operators; processes, not powers. The Law of Gravitation, for instance, speaks to science only of process. It has no light to offer as to itself. Newton did not discover Gravity--that is not discovered yet. He discovered its Law, which is Gravitation, but tells us nothing of its origin, of its nature or of its cause.