Page:The Solar System - Six Lectures - Lowell.djvu/61



done in a given time by tide-raising forces, we have, then, $$\textstyle (\frac{2m\rho}{r}+\frac{3m\rho^{2}}{r})^{2}$$ or for most cases sufficiently well, taking only the first term, $$\textstyle \frac{4m^{2}\rho^{2}}{r^{6}}$$ That is, it is as the square of the attracting mass and the square of the radius of the affected body directly and inversely as the sixth power of the latter's distance.