Page:On an inversion of ideas as to the structure of the universe.djvu/17

 of the problem of the universe. The first of these steps was taken in 1874, with the object of finding a mechanical explanation of the sudden change in the rate of flow of the gas in the tubes of a boiler when the velocity reached a certain limit; perhaps this would be better described as a step towards a step.

The second step was the discovery of the thermal transpiration of gas, together with the analytical proof of the dimensional properties of matter.

The third step was the discovery of the criterion of the two manners of motion of fluids. . And it was only on taking the fourth step, namely, the study of the action of sand, which revealed dilatancy as the ruling property of all granular media which directed attention to the possibility of a mechanical explanation of gravitation. In spite of the apparent possibility, all attempts to effect the necessary analysis failed at the time.

There was, however, a fifth step; the effecting of the analysis for viscous fluids, and the determination of the criterion, which led to the