CHEMISTRY. Chemistry may be briefly defined as the study of the laws of the phenomena of composition and decomposition, which result from the molecular and specific mutual action of different substances, natural or artificial. In the observations of chemistry the senses are still more employed, and experiment is of still more utility. Even in chemistry metaphysical conceptions, such as "affinity," linger. PHYSIOLOGY. Physiology may be defined as the study of the laws of organic dynamics in relation to structure and environment. Placed in a given environment, a definite organism must always act in a definite way, and physiology investigates the reciprocal relations between organism, environment, and function. In physiology observation and experiment are of the greatest value, and apparatus of all kinds is used to assist both observation and experiment. Physiology is most closely connected with chemistry, since all the phenomena of life are associated with compositions and decompositions of a chemical character. _II.--Social Physics_ To place social physics on a scientific basis is a task of great difficulty, since social theories are still perverted by theological and metaphysical doctrines. All I can hope to do is to point out general principles which may serve to correct the intellectual anarchy which is the cause of the moral and political anarchy of the present day. I propose to state first how the institution of a science of social physics bears upon the principal needs and grievances of society, so that men worthy of the name of statesmen may realise that such labours are of real utility. So far, positive philosophy has worked timidly and tentatively, and has not been bold and broad and general enough to cope with intellectual anarchy in social questions; but it is necessary now that it play a more dominant part in life, and lead society out of the turmoil in which it has tossed for three centuries. At present, society is distracted by two conflicting influences, which may be called the theological polity and the metaphysical polity. The theological polity at one time exercised a beneficent influence on society; but for three centuries past its influence has been essentially retrograde, and has gradually, but radically, decayed. The causes of its decline are various; but the chief present-day antagonist to the theological polity is the scientific spirit, and the scientific spirit can now never be repressed. The metaphysical polity is progressive, but progressive mainly in a negative way. So far, it has made for progress; but it has made for progress chiefly by removing impediments to progress, by destroying the theological conceptions which retarded the development of human intelligence and human society. Though dangerous and revolutionary, it has been necessary; for much required to be demolished to permit permanent reconstruction.