the molecular forces. The consequence of this was another step forward, of the greatest possible importance. It was shown that the physical forces are as obedient to quantitative laws as matter itself had been proved to be, and that, while they are mutually convertible into each other, force, like matter, is indestructible in its nature. The various forms of energy by which effects are produced in the surrounding world, although changing incessantly, were discovered to be never created and never annihilated. With the evidence that every form of force is derived from some preexisting form of it, the hope of a mechanism generating its own power perpetually, passed away among impossibilities, and the science of forces became limited to problems of transformation. It was much to have exploded the fallacy of the perpetual motion, upon which the ingenuity and wealth of generations had been wasted, but it was far more to have seized upon a principle of Nature which Dr. Faraday could pronounce to be the highest law in physical science which our faculties permit us to perceive. And are the discoverers of this principle to be held accountable for the reach and play of its applications? No doubt a law of Nature's activities, thus supreme and far-extending, cannot be limited to the field of physical phenomena. The probabilities are strong that, wherever effects are produced in degrees of more or less, they are strictly conformable to quantitative conditions, although the proof of it may be indirect and difficult, and exact results quite unattainable. But with this point we have here no concern, and only say that it is no business of Science if the law be found to pervade domains of thought which Philosophy has hitherto claimed to be exclusively her own. Nor is there any just ground for arraigning men of science as transgressing the proper limits of their inquiries by pursuing the principle of the conservation of energy into the spheres of life, mind, and social activity. Science could not evade the necessity of entering upon the earlier steps of the investigation, any more than it can now evade the necessity of pursuing it; and it would be a worthier proceeding on the part of philosophers, gratefully to accept what she contributes for their use, rather than to raise an outcry against the scientists for interfering with matters which, it is assumed, do not belong to them.
The work of putting down Herbert Spencer, which has been going on these dozen years, still flourishes and threatens to become a regular occupation. Obscure men are making reputations right and left, and famous men are adding to their laurels by taking down the great philosopher on all sides. If they do not succeed in getting him out of the way, this branch of criticism may grow into a thrifty business. Who shall be greatest in this little but increasing kingdom of criticism, it is as yet premature to say, although symptoms of gradation in the honors of the work are beginning to be disclosed. We explained, some time since, in the Monthly, that our friend Liefchild had brought forth a big book, which was evidently designed to interrupt Mr. Spencer's philosophical career. He did not, however, himself aspire to the distinction of wiping him out, but assigned that high function to President Porter, of Yale, whom he ranked as the great "Spencer-crusher." Mr. Liefchild would probably accord to others the minor grades of extinguishers, upsetters, depresses, etc. Meantime the work may be expected to proceed vigorously. Although we often hear that Mr. Spencer has at last been quite demolished and put an end to, he seems to be still alive and in a very vigorous condition, as the article replying to the Quarterly Reviewers in our present number will