138 Reports & Proceedings — Geological Society of London. 



A singular feature, which seems difficult to reconcile with its use 

 as an implement, is the restriction of tlie flaking on one edge to the 

 weathered crust. 



The origin of the flaking is discussed, and the author, while 

 admitting that the fashioning of the flint is not inconsistent with 

 intelligent design, concludes that the evidence is not sufficient to 

 establish this beyond dispute. It is eminently a case of "not proven". 



The Secretary read a letter from Mr. J. E.eid Moir, in which he 

 stated that the flint in question was found by him in the detritus- 

 bed below the decalcified Crag in tlie brickfield of Messrs. Bolton 

 and Co., Henley Road, Ipswich, and that the author at first accepted 

 the specimen as being of undeniable human origin. Mr. Eeid Moir 

 further expressed the opinion that the flaking to be seen upon the 

 specimen was " human " in its characteristics, and referred to his 

 printed papers in support of that opinion. 



3. Felruary 6, 1918.— Dr. Alfred Harker, F.KS., President, in the 



Chair. 



The following communication was read : — 



"Some Considerations arising from the Frequency of Earthquakes." 

 By Eichard Dixon Oldham, F.Ii.S., F.G.S. 



The publication ^ of an abstract of twenty years' record of earthquakes 

 in Italy gives an opportunity for studying the effect of the 

 gravitational attraction of the sun ; the period is so nearly coincident 

 with the lunar cycles of 19 and 18 "6 years that the effect of the 

 moon may be regarded as eliminated, the record is of exceptional 

 continuity and completeness, and the number of observations is large 

 enough to allow of the extraction of groups sufficiently numerous to 

 give good averages. 



The distribution of the stresses is dealt with in textbooks ; there 

 is a maximum upward stress, in diminution of the earth's attraction 

 at its surface, at the two points where the sun is in the zenith or 

 nadir, and a maximum downward stress along the great circle where 

 it is on the horizon ; but as, for the purpose of this investigation, 

 a decrease of downward pressure is equivalent to an increase of 

 upward, I shall take the line along which the downward stress is 

 greatest as the zero-line, and express the amount of stress at any 

 other time or place as a fraction of the difference between the net 

 force of gravity along this line and at the point where the sun is in 

 the zenith. The fraction, at any given time and place, depends 

 solely on the zenith distance of the sun, which is continually varying 

 with the revolution of the earth. At the equinox, when the sun is 

 on the equator, the curve of variation between 6 a.m. and 6 p.m. is 

 the same as in the other half of the day ; at any other part of the 

 year it is not symmetrical in the two halves of the day, but is the 

 same during the day in the summer half of the year as during 

 the night in the corresponding part of the winter half, when the 

 declination of the sun is equal in amount, though opposite in 

 direction. 



^ Boll. Soc. Sismol. Italiana, vol. xx, p. 30, 1916. 



