The hachured hills are based upon contours, and are of admirable commensurability.
The long-sought cause of the "great inequality" of Jupiter and Saturn was found in the near approach to commensurability of their mean motions; it was demonstrated in two elegant theorems, independently of any except the most general considerations as to mass, that the mutual action of the planets could never largely affect the eccentricities and inclinations of their orbits; and the singular peculiarities detected by him in the Jovian system were expressed in the so-called "laws of Laplace."
A periodic character was thus indicated for the disturbance; and Laplace assigned its true cause in the near approach to commensurability in the periods of the two planets, the cycle of disturbance completing itself in about goo (more accurately 929) years.
For a normal field, the commensurability oscillations are weak and out of phase for transport in the different cleavage directions.
The commensurability oscillations behave exactly as predicted in a recent theory of two-dimensional surface superlattices.
