Page:Lectures on Ten British Physicists of the Nineteenth Century.djvu/106

and deduced that Sirius is receding from the Sun at the rate of 30 miles per second. Stokes closed his address with some observations on life and mind these being characteristic of his philosophical attitude which was that of the golden mean. He says "What this something which we call life may be, is a profound mystery. We know not how many links in the chain of secondary causation may yet remain behind; we know not how few. It would be presumptuous indeed to assume in any case that we had already reached the last link, and to charge with irreverence a fellow worker who attempted to push his investigations yet one step farther back. On the other hand, if a thick darkness enshrouds all beyond, we have no right to assume it to be impossible that we should have reached even the last link of the chain, a stage where further progress is unattainable, and we can only refer the highest law at which we stopped to the fiat of an Almighty Power. . . . When from the phenomena of life we pass on to those of mind we enter a region still more profoundly mysterious. We can readily imagine that we may here be dealing with phenomena altogether transcending those of mere life, in some such way as those of life transcend, as I have endeavored to infer those of chemistry and molecular attractions, or as the laws of chemical affinity in their turn transcend those of mere mechanics. Science can be expected to do but little to aid us here, since the instrument of research is itself the object of investigation. It can but enlighten us to the depth of our ignorance and lead us to look to higher aid for that which most nearly concerns our well-being."

In 1880 the Cambridge University Press began the republication in collected form of Stokes' Mathematical and Physical Papers. In this publication he introduced for the first time the solidus notation for division, originally introduced by De Morgan in his article on the Calculus of Functions in the Encyclopædia Metropolitana. If a fraction like ${\frac {a}{b}}$, or a differential coefficient such as ${\frac {dy}{dx}}$ is mentioned in the text, the printing of such expres-