78 G Geological Society: — 



between the Eissingtons and Burford.' By Linsdall Richardson, 

 F.G.S. 



3. ' The Flora of the Inferior Oolite of Brora (Sutherland).' By 

 Miss M. C. Stopes. D.Sc, Ph.D. 



4. 'The Constitution of the Interior of the Earth as revealed 

 by Earthquakes (Second Communication) : Some New Light on the 

 Origin of the Oceans.' By Eichard Dixon Oldham, F.G.S. 



The attempts, which have been made to account for the oceans 

 and continents, are all subject to an uncertainty, in that we 

 have had no means of knowing whether it is a mere irregularity of 

 form that has to be accounted for, or whether this irregularity is 

 but the expression of a deep-seated difference in the constitution of 

 the earth. The paper is an attempt to clear up this uncertainty by 

 a comparison of the European records of the San Francisco and 

 Colombian earthquakes of April 18th and January 31st, 1906. In 

 the former case the wave-paths to Europe lay under the continent of 

 North America and the continental shelf of the North Atlantic, 

 being typically continental in character; in the latter case they 

 crossed the broadest and deepest part of the Atlantic basin, being 

 essentially oceanic. The absolute rates of propagation cannot be 

 compared, owing to the time of occurrence of the Colombian earth- 

 quake being unknown ; but the interval between the arrival of the 

 first and second phases is found to be longer in the case of this 

 earthquake, by an amount much in excess of any probable error of 

 record or interpretation. This difference indicates that the rate of 

 propagation of the second-phase waves was relatively slower in the 

 case of the Colombian earthquake, and, consequently, a difference 

 in the constitution of the matter through which they were propa- 

 gated. The Japanese records of the San Francisco earthquake also 

 give an interval between the first and second phases which is greater 

 than the average, the wave-paths in this case too being oceanic. 



From these facts the general conclusion is drawn, that oceans and 

 continents are not mere surface-irregularities of the earth's form, 

 but are accompanied by, and probably related to, differences in the 

 constitution of the earth beneath them, which extend to a depth of 

 about one-quarter of the radius. It is not possible to state exactly 

 in what this difference consists, beyond that it causes the rate of 

 propagation of the second-phase waves to be less, in comparison 

 with that of the first-phase waves, under the oceans than under 

 the continents. 



5. ' The Swansea Earthquake of June 27th, 1906.' By Charles 

 Davison, Sc.D., F.G.S. 



With the exception of the Hereford earthquake of 1896, the 

 Swansea earthquake was the strongest which has been felt in this 

 country for more than 20 years. It disturbed an area of 66,700 

 square miles, reaching from Eochdale on the north to Penzance on 

 the south, and from beyond Maidenhead on the east to Waterford 

 on the west. The centre of the isoseismal .8 lies about. 3 miles 

 west of Swansea, the longer axis of the curve being directed E. 5° N. 

 and W. 5° S. At Swansea, Neath, etc., the total number of chimneys 

 thrown down or damaged must amount to several hundred. 



