As admonitions to cross-examine and to sift facts and phenomena they are valuable.

Many of the observations and classifications are subtle and instructive.

But in his hands nothing comes of them.

They lead at the utmost to mere negative conclusions; they show what a thing is not.

But his attempt to elicit anything positive out of them breaks down, or ends at best in divinations and guesses, sometimes--as in connecting Heat and Motion--very near to later and more carefully-grounded theories, but always unverified.