The power by which the parts of bodies are kept together. It is a phenomenon the most common, but the least understood. Newton derides the hooked atoms, by means of which it has been attempted to explain coherence; for it still remained to be known why they are hooked, and why they cohere. He treats with no greater respect those who have explained cohesion by rest. “It is,” says he, “an occult quality.”

He has recourse to an attraction. But is not this attraction, which may indeed exist, but is by no means capable of demonstration, itself an occult quality? The grand attraction of the heavenly bodies is demonstrated and calculated. That of............