Or we see the molar motion of a student's hands bringing together some acid and two metals. At once chemical action, a form of molecular motion, is set up. The molar motion of hands, a piece of silk, and a glass rod results in electricity, a mode of molecular motion. Or we apply heat, a mode of molecular motion, to a bar of metal which expands, to a mixture of hydrogen and oxygen which unite chemically. Or to a crystal of tourmaline, one end of which becomes positively electric, the other negatively. These are all cases of the transformation of motion without any creation or destruction. In all these cases the amount of matter and the amount of motion remain unchanged. Only the quantities of particular kinds vary. The generalisation that the quantity of matter and motion in the universe is the same yesterday, to-day, and for ever, appears to be thoroughly established. More than this. Not only is there no scientific basis whatever for the fancy of a creation or of a destruction of matter or of motion. The fancy is unthinkable. No human mind is capable of picturing to itself the passage from the material to the immaterial, the moment of time in which the non-universe began to be the universe. Yet again. Up to the present time every explanation of every phenomenon of the universe has been in terms of matter and of motion. The law of gravitation, Kepler's three great generalisations in astronomy, the phenomena of attraction and repulsion in electrified and magnetised bodies, the nature of chemical elements and compounds, the relation between, plants and animals in regard to their effect on the air, the principles of variation, of natural selection, of heredity, of adaptation--these and thousands of other truths that unseal our eyes to the beautiful meaning of nature, are all explanations as to how certain forms of matter are in certain states of motion. And if up to the present hour all the explanations that have been forthcoming of natural things are in terms of the natural, we are entitled to conclude that all explanations hereafter will be in kindred terms. Or we may look on the question in another way. In the days of man's greater ignorance everything was primarily or ultimately referred to the supernatural. All phenomena were at first directly due to the action of the supernatural. But, as time and knowledge advanced, these references grew fewer and fewer in number. They were replaced by perfectly natural explanations of events, and we are entitled to believe that this process of elimination has now gone on sufficiently far for us to hold that since super-naturalism is unnecessary for the primary explanation of phenomena, it is also unnecessary for their ultimate explanation.