SECTIONAL TRANSACTIONS.— G, H 385 



produced by the forces which it replaces. Similarly, resuitarit stresses produce 

 the same effects (strai.is) which are produced by the stresses which they replace. 

 This idea is carried through in the present paper. A series of points in a 

 solid are fi.xed upon and expressions set up which determine the relative dis- 

 placements of these points if subjected to a number of stresses acting in various 

 directions. These expressions contain terms which depend only on the intensi- 

 ties of the stresses and their directions, and not on the relative position of 

 the selected points. These terms must be fulfilled by the resultant stresses, 

 and thus a number of formuhe are obtained which determine the intensities and 

 directions of the resultant stresses. Vector co-ordinates are employed. For 

 stresses acting parallel to a single plane the simple rule is evolved that, adopting 

 an arbitrary direction, all the angles which the stresses make with this direc- 

 tion must be doubled, and a polygon of stresses is then constructed with these 

 doubled angles. The end-points of this polygon may be looked upon as being 

 the foci of an ellipse or of a hyperbola, whose major axes are equal to the 

 algebraic sum of the stresses. The direction has to be halved. This result 

 can, of course, be obtained from the formute evolved with the help of the law 

 of acceleration. The papor also deals with the resultants of stresses in space. 

 The paper explains the use which can be made of this method of resolving 

 stresses for measuring the strains in celluloid which are revealed by polarised 

 light. 



10. Mr. E. S. Whipple. — Demonstrafion of the Collins Micro- 

 Indicator for high-speed Engi)ies. 



SECTION H.— ANTHROPOLOGY. 



(For references to the publication elsewhere of communications entered in the 

 following list of transactions, see p. 409.) 



Thursday, September 7. 



1. Presidential Address by Mr. H. J. E. Peake on The Study of 



Man. (See p. 150.) 



2. Dr. Cyril Fox. — The Distribution of Population in the Cambridge 



Region in Early Times, with special reference to the Bronze 

 Age. 



The distribution in Britain of constructions attributable to the Neolithic 

 and Early Bronze Ages suggests that the population w;is then limited to those 

 areas, mainly upland, which must have been, under natural conditions, largely 

 free from forest. 



A topographical analysis of finds and remains of all culture periods from the 

 Neolithic to the Saxon in a limited area — the Cambridge Region — was under- 

 taken to determine w-hether this limitation was complete or partial, and when 

 the clearing and occupation of forest areas commenced. The Cambridge Region 

 is very suitable for the inquiry, since it possesses a wide range of soils and has 

 yielded numerous finds of all periods. 



The maps exhibited suggest (1) that the chalk belt and the eastern shore- 

 line of the Fens were occupied from Neolithic times onwards ; (2) that there 

 was a gradual shift of population from N.E. to S.W., i.e. from the West 

 Suffolk heathland to the fertile lands of the upper Cam and Ouse valleys, as 

 agriculture developed ; and (3) that the forest uplands were almost entirely 

 unoccupied until the Roman period. 



The distribution of population in the Bronze Age is, generally speaking, 

 of a character intermediate between that of the Age which preceded it and 

 that which followed, but it presents features of special int-erest. 



