of heat, linked with the biology by being based largely on "open-air" problems. It starts, for example, with a study of the thermometer as an instrument by means of which the varying coldness and warmth of the air may be unambiguously determined and recorded objectively. Its use for this purpose has hitherto been accepted as part of the nature of things, but we now raise the question, How does the thermometer work? and are thus led to the consideration of expansion as a phenomenon that generally accompanies heating. The reader should notice this inversion of the usual order of treatment, for it is typical of the methods recommended throughout the syllabus. That is to say, what are usually treated as applications of physical principles first taught in some other connection, are here taken as starting-points from which the principles themselves are derived by analysis: the theory is derived from the applications rather than the applications from the theory. It is, however, important to add that the theory, once established, is used as a clue to the understanding of further and more complicated applications. Another inversion of customary procedure may also be mentioned. Instead of graduating the thermometer-scale by reference to "fixed points,' we accept and copy the standard graduation of the shop-made thermometer, and afterwards enjoy the striking discovery that the temperature of water during boiling or freezing is constant. This is a simple instance of the principle--always a useful guide though never to be followed slavishly or pedantically-that the historical order of discovery generally indicates the best order of exposition.

In the third year the simple ideas on radiation and conduction, gained by studying the school hot-water

system during the previous session, are sharpened into more precise concepts by observation of the seasonal temperature-changes of the soil and kindred phenomena. From these it is a natural transition to the study of the sun's radiation as the primal source of the energy expressed in plant and animal life. We come thus to the prism, the solar spectrum-visible and invisible, photometry, the laws of radiation and absorption of light and heat with their important utilitarian applications, the properties of plane and curvedmirrors, and the laws of refraction of light.

At this point we pass to the conception of heat as a measurable quantity, and, following the simple methods of the pioneer investigator, Joseph Black, reach clear ideas about specific heat and the latent heat released or absorbed in changes of state. The ideas thus won are used to explain the behaviour and economy, first of internal combustion engines (petrol "motors" and gas-engines) and then of the older cylinder steam-engine and the modern turbine. This excursion into engineering involves a study of the expansion of gases under isothermal and adiabatic con- tit ditions and of the epoch-making investigations of Joule into the equivalence between heat and mechanical work.

The pupil receives at the same stage his introduction to the fascinating science of electricity. Beginning with the dissection of the electric bell, he is led at once to electro-magnetism and the electric motor, telegraphy and the galvanometer being taken en route. Faraday's classical experiments on electro-magnetic induction bring him to the induction coil and the dynamo, and a little later to the telephone. The reciprocal relations between the motor and the dynamo are

emphasized, and are made the occasion for enlarging his ideas about the transformation of energy-a subject which receives further illustration, first from a study of electric lighting, and finally from a comparison between the modes of action of secondary and primary batteries.

It is to be observed that the treatment of electricity during the third year is almost entirely "qualitative in character. The aim is to make the fundamental notions of the science clear by a study of their most familiar and interesting applications. It is obviously impossible to discuss the dynamo and the transformer, electric lighting, and secondary batteries without speaking of electromotive force and resistance, of "volts and "ampères," but there is no need at this stage to give precise definition to those terms. It is enough to use them with the practical understanding which is sufficient for the person who has to buy a new lamp for his house or a new accumulator for his motorcycle. The task of investigating the theory of electrical measurements is reserved for the fourth year, where it forms an important item in the session's work.

From the theory of electrical measurements we pass to the geometrical theory of optical measurements. This, in turn, is followed by a simple exposition of wave-theory, applied to bring the undulatory phenomena of sound, light, heat and electricity under the domination of one of the most far-reaching and illuminating of scientific conceptions.

The course is planned to conclude with a simple account of the discoveries about radioactivity which form the present "growing-point" of electricity, and of the "theories of matter" based on them, followed

by a general review of physical phenomena from the standpoint of the conservation of energy and with special reference to the sources and economical use of the energy available for the world's work. As in the parallel case of biology, it is suggested that these subjects should, where possible, be reserved for a series of discussions in the course of the fifth year.

The three-years course in chemistry is developed in much the same way as the physics. Simple problems concerning the economy of plant-life largely determine the earlier course of the chemical argument, while the later work generally takes the form of an inquiry into the principles underlying familiar chemical processes and industrial applications of universal importance. The course is, therefore, broad rather than deep; details of secondary importance being omitted and attention concentrated on the typical conceptions and methods of organic as well as inorganic chemistry. As in the case of the sister subject, general theories are postponed to the fourth year, and the course ends with a review of the present condition of chemical science and industry-preferably to be postponed to the fifth year in which special emphasis is laid on the social importance of pure scientific research and on the necessity for bringing exact knowledge to bear on the problem of utilizing the common riches of the natural world for the benefit of all mankind.

It remains to indicate the aims and scope of three subordinate sections of the scheme not hitherto mentioned. The first is a course which, beginning under the title "General Physics," develops in the third and fourth years into a formal study of the principles of mechanics. In the first In the first year the young student, after learning to use the physical balance to measure den

sities and specific gravities, is invited to study the mechanism of that important instrument and the conditions determining its accuracy and sensitiveness. In this way he comes to the theory of the lever and the centre of gravity. Next, in connection with the problem of measuring time-of which something is to be said below-he examines the mechanism of that familiar but little-understood instrument, the clock,. and makes simple experiments on the pendulum. The examination of other common pieces of mechanism, such as locks and the "three-speed" gear of the bicycle, gives him further useful and congenial employment, and the year's work concludes with an elementary study of the mariner's compass and magnetism.

In the second year, the hydrostatics of the previous session is continued by an inquiry into the flotation of ships leading to the discovery of Archimedes' Principle and to the theory of pontoons, submarine navigation and balloons. The study of the barometer as a meteorological instrument gives an opportunity for retracing a classical route of scientific exploration from Torricelli, through Pascal to Robert Boyle, on which discoveries were made which prove explanatory of a great variety of useful appliances and inventions, ancient and modern. Capillarity and osmosis 1 are studied by simple experiments as problems arising in the investigation of plant-life. Towards the end of the year the pupil passes from levers to pulleys, learns how to estimate their "efficiency," makes measurements of friction, and becomes acquainted with the "principle

1 For capillarity the teacher may profitably consult Worthington, The Splash of a Drop (S.P.C.K., 1907), and C. V. Boys, Soap Bubbles (S.P.C.K., 1912); and for osmosis, Osterhout, Experiments with Plants (Macmillan, 1906).