358 SECTIONAL TRANSACTIONS.—A, A*. 
Mr. S. F. MarKHam.—The meteorological basis of civilisation (12.0). 
Recent factory experiments on both sides of the Atlantic have proved 
conclusively that there are certain conditions of temperature, humidity and 
air movement under which workers are at their most efficient and most 
energetic. On the other hand, recent investigations into the ‘ poor white’ 
problem show that even the best racial stocks quickly lose in energy and 
efficiency, and even in moral fibre, when subjected continuously to tem- 
peratures and humidities well above the ideal. Human efficiency and 
energy therefore have a distinct climatological basis, and the history of 
civilisation follows extraordinarily closely man’s control of indoor tempera- 
tures and humidities. Investigations are to a certain extent handicapped 
by the absence of reliable statistics for radiation and air movement, and by 
the absence of any instrument which accurately records bodily sensations of 
comfort or discomfort. 
Taking, however, meteorological information from all parts of the world, 
the paper shows that the civilised portions of the world to-day all enjoy 
certain conditions of climate and climate control, and that in the past great 
civilisations have only arisen where there has been an approximation to these 
conditions. 
Dr. E. C. BULLARD.—Gravity determinations in East Africa (12.30). 
A series of gravity measurements has been made in E. Africa by a method 
which enables a large number of results to be obtained in a short time. The 
observed value of gravity over the plateau is found to be less than that 
calculated from the assumption that the surface features are simply resting 
on the crust. The natural interpretation of this is that the plateau is iso- 
statically compensated, that is, that it is underlain by light matter which 
projects downwards into the denser substratum and supports the typo- 
graphy in the same way as an iceberg is supported by its roots. 
Over the Rift Valleys a further deficiency of gravity is found ; they are, 
therefore, underlain by more light matter than is required for isostatic 
equilibrium, and if gravity and hydrostatic forces were given free play their 
floors would rise. ‘This means that they must be held under by the plateau 
on each side, which can only occur if there is sideways pressure. ‘The 
Rift floor cannot have ‘ fallen in,’ for if released it would rise, not fall. The 
gravity results, therefore, give what seems a conclusive decision between 
the ‘ tension’ theory of Gregory and the ‘ compression ’ theory of Wayland. 
DEPARTMENT OF MATHEMATICS (A*). 
Monday, September 9. 
Prof. W. H. McCrea.—An attempt to examine the relation between 
physical postulates and mathematical axioms in general mechanical 
theories (10.0). 
The general problem of the use of geometry in physics. The physical 
basis for the use of Riemannian geometry in general relativity, and its 
generalisations in Weyl’s geometry and in projective relativity. The 
construction of a geometry from physical postulates as carried out by 
A. A. Robb. 
Procedure from postulates concerning the relations of matter rather 
than space time as carried out by E. A. Milne. 
