of the _Mecanique celeste_ of Laplace, published in 1804 and 1805, and he might, no doubt, have thought that before long mathematics would enable physical science to develop with unforeseen safety.
All these results may doubtless be compared in importance with the present discoveries.

When strange metals like potassium and sodium were isolated by an entirely new method, the astonishment must have been on a par with that caused in our time by the magnificent discovery of radium.

The polarization of light is a phenomenon as undoubtedly singular as the existence of the X rays; and the upheaval produced in natural philosophy by the theories of the disintegration of matter and the ideas concerning electrons is probably not more considerable than that produced in the theories of light and heat by the works of Young and Rumford.
If we now disentangle ourselves from contingencies, it will be understood that in reality physical science progresses by evolution rather than by revolution.

Its march is continuous.

The facts which our theories enable us to discover, subsist and are linked together long after these theories have disappeared.