In reviewing the history of the onward march of chemistry in the past, we find that Robert Boyle, who lived from 1627 to 1691, was the first chemist who grasped the idea of the distinctions between an elementary and a compound body. He has been called the first scientific chemist, and he certainly did much to advance chemical science, particularly in the borderland of chemistry and physics, but he did this more by his overthrow of false theories, than in any other way. It was left for Scheele (born 1742), an obscure Swedish chemist whose discoveries extended over the whole range of chemical science, and his French contemporary, Lavoisier (born 1743), to bring about a complete revolution in chemistry. Thus, step by step, and period by period, experimental science has prepared the way to reach that elevation which humanity is destined eventually to attain, when all errors have been discarded and truth reigns triumphant. The question has been asked, in view of the past history of discovery, what may not the science of the future accomplish in the unseen pathways of the air? That still unconquered field lies before us, and we know that it is only a question of time when man will hold dominion there with as firm sway as he now holds it on land and sea. Physics and chemistry walk hand in hand. Scientists cannot cut the tie that joins them together in experimental science. Physics treats of the changes of matter without regard to its internal constitution. The laws of gravitation and cohesion belong to physical science. They concern matter without reference to its composition. Chemistry makes us acquainted with the constituents of the different forms of matter, their proportions and the changes which they are capable of bringing about in each other. But notwithstanding the lessons of the past, both chemistry and physics are blind to what the future has in store for them. Scientists have erected barriers to progress, building them so as to appear of solid masonry on the ground of false hypotheses; but, when the hour is ripe, these will be swept away as if by a cyclone, leaving not one stone on another. It was Boyle who overthrew the so-called Aristotelian doctrine, and Paracelsus's teachings of the three constitutents of matter, disputed first by Van Helmont. Boyle taught that chemical combination consists of an approximation of the smallest particles of matter, and that a decomposition takes place when a third body is present, capable of exerting on the particles of the one element a greater attraction than is exercised by the particles of the element with which it is combined. In this conjecture there is just a hint of the grand potentialities in the unknown realm which is now being explored by Keely, the discoverer of the order of vibration that releases the latent force held in the interstitial spaces of the constituents of water; one order of vibration, being more in sympathy with one of the elements of water than with the other, possesses a