since, was the first clear enunciation of the generalisation towards which so many observations had led. When he reminded men that chemical action, electricity, heat, sound, light, magnetism, and life were all convertible, one into the other, and thus convertible in definite numerical proportions, mathematically calculable, the keynote of the idea of Evolution had been struck.

Harsh as it may seem, an idea in any branch of knowledge has never attained a sure basis until it is expressible in terms of mathematics. There was a time when physics and chemistry were divorced from mathematics to a large extent. Now even the phenomena of electricity and the reactions one upon another of chemical bodies are expressed in algebraical formulae. This is the result of the increased precision of our knowledge. Following in the footsteps of physics and chemistry the biological sciences are becoming every day more mathematical. We have formulas to express the manner of the arrangement of leaves upon a stem, the manner of arrangement of the parts of a flower. One of these days every structural and functional fact in regard to every living thing will be related to some formula of mathematics more or less general. We shall not all become martinets or dryasdusts. There is a beauty in exactness. I sometimes think that the difference between the loveliness of our thinking and of our dreaming on natural phsenomena, as compared with that which the older thinkers and dreamers enjoyed, will be as the difference between the joy of a game of chess between skilled players or between those that know not even the moves. The child pushes the kings and queens and rooks and knights and bishops and pawns about at random, and laughs gaily. But the master' of the game, moving them according to definite rules, obtains a far higher enjoyment, and produces a combination that has its poetry.

The very sciences that deal with these different modes of matter and motion are now by no means as clearly marked off one from another as their earlier students thought they were. Physics, chemistry; geology, botany, zoology, anatomy, physiology, how they all dovetail into, or actually overlap each other. It is impossible to say sometimes to which domain of science a particular fact belongs. The distinctions between the physical and the chemical properties of bodies are confessedly artificial. Botany implies a study of the anatomy and the physiology of plants. Physiology in its turn becomes only a question of chemistry; its phenomena are becoming reduced to mathematical expressions. We are learning to calculate the actual amount of work done in the performance of different functions of the living body, in the same terms as we calculate the work done by a steam engine. The respiratory organs or the muscular during the day do so many foot-pounds of work. The foot-pound is the unit of measurement employed in the study of work. Work is done when matter is moved through space. The footpound is the amount of work done when the mass of a pound is raised one foot against the gravitation attraction of the earth. A steam-engine does per day a certain number of foot-pounds of work. Its capacity for work is usually expressed by saying that it is so many horse power. One horse power is equivalent to 33,000 footpounds per minute. The physiologists are, by means of very intricate and careful calculations, enabled to calculate with ever-increasing accuracy the equivalent in footpounds, i.e., the mechanical equivalent, of each of the body functions of the average man per diem.

If we turn to any of the special sciences the same dovetailing and over-lapping appear. In chemistry it is difficult to mark off any group of bodies from all other groups. The three sets of bodies that chemistry is supposed to study are elements, mixtures, and compounds. An element such as carbon or gold, is a body which has not yet been decomposed. A mixture is that which results from putting together two or more substances, without those substances undergoing any