180 REPORTS ON THE STATE OF SCIENCE.—1917. 
the earth, and to be thrilled at the discovery of the parallax of some of the 
fixed stars. The scope of the course must vary greatly with the ability of the 
class and with its mathematical knowledge, but it must not only deal with the 
solar system, but give an idea of the magnitude of the Universe as a whole. 
Theories of the origin of the solar system, the history of the earth and its 
movements, may lead naturally to a discussion of the seasons, of early modifi- 
cations of the earth’s crust, and of the great wind belts. 
Such a course as this may run concurrently with a course of experimental 
work on light, the two sets of lessons being constantly linked together. 
Very simple experiments showing propagation of light in straight lines, 
formation of shadows, reflection and refraction will lead on to the study of 
the eye, and of optical instruments and their use in the observatory. Colour, 
the wave theory of light, and means of measuring the velocity of light can 
also be simply dealt with. 
IV. Ages 15 and 16.—During the last two years of the general school course 
the pupils should be introduced to some of the theories which dominate 
scientific thought at the present day. They should realise how great theories 
grow—the industrious collection of data, the leap forward of some master- 
mind to grasp the deeper truth which underlies and unifies the apparently 
disconnected facts, the laborious process of verification. (a) The object of the 
first term’s work is to bring forward the wide conception that all forms of 
energy are convertible one into another, and that the great mechanical devices 
which have been invented are methods of converting the forms of energy into 
the most useful kind for any special piece of work. It may also form an intro- 
duction to the study of magnetism and electricity and show how the electric 
power used in every-day life is generated. For example, it is quite easy to 
measure the mechanical equivalent of heat, to show how chemical energy can 
be used to generate electric energy, and to show how electric energy can cause 
chemical change. In the study of the dynamo, magnetic and electric energy 
can be shown to help each other’ and to produce heat, light, and mechanical 
work. This will lead to a discussion of the working of electric trams, the 
production of electric light, and of much else. (b) The cbject of this part of 
the course is to obtain experimental results which lead on to an understanding 
of the general theories with regard to the constitution of matter, 
The experiments can be made to develop in a logical sequence starting from 
the study of air and the oxides. They can be carried out both qualitatively 
and quantitatively, leading to the knowledge of the quantitative nature of 
chemical action and also to the properties of many substances—e.g., acids, 
alkalies, and salts. Equivalent weights of some of the elements may be found 
by simple but accurate work. 
A possible arrangement of this experimental work is as follows :— 
1. Chemical changes caused by heating substances in air. 
2. Chemical changes due to heating substances out of contact with air. 
3. Chemical changes due to the action of substances on each other. 
When new substances are discovered their properties can be investigated and 
the history of the discovery in many cases given. 
An important bit of work which should not be omitted in a course of this 
kind is the application of chemical properties of substances used in every- 
day life—e.g., the softening of water, the preparation of explosives and fertilis- 
ing agents, the comparison of baking-soda and washing-soda, the manufacture 
of matches. &c. But these will be side issues. 
The collection of experimental results and a discussion of the explanation of 
these will give rise to an historical treatment of the molecular and atomic 
theory, Dalton’s work being dealt with. The newer theories of the constitution 
of matter and their bearing on the older theories may then be discussed. The 
theoretical explanation of many results obtained in the early part of the course 
now becomes evident, and facts which had hitherto appeared disconnected and 
comparatively meaningless are suddenly seen to be intimately connected and 
interdependent; a new mental outlook is reached which both transforms the 
view of knowledge already obtained and suggests fresh problems to attack. 
V. Ages 17 and 18.—No gir] should leave school without some acquaintance 
