1890.] On the British Earthquakes of 1889. 275 



the rise of blood pressure respiration occurred, even although a much 

 higher intracranial tension was maintained than had been sufficient 

 to arrest it when the blood pressure was lower. 



II. By the direct application of pressure in the upper part of the 

 4th ventricle a slowing of the heart with a rise of blood pressure was 

 caused, whilst rapid respiration continued, so rapid as even to be 

 nearly three times the rate of the heart in some cases. Pressure 

 below the calamus scriptorius arrested the respiration without 

 directly influencing the heart, whilst in the lower part of the 4th 

 ventricle respiration was impeded or arrested along with a fall in 

 blood pressure, and some slowing of the heart, followed by arrest, 

 after the respiration had ceased. 



Numerous observations are recorded which are, in many cases, 

 combinations of the foregoing, and therefore not suitable for con- 

 densation in this abstract. 



Tracings are furnished illustrating each point advanced. 



X. "On the British Earthquakes of 1889." By CHARLES 

 DA.VISON, M.A., Mathematical Master at King Edward's 

 High School, Birmingham. Communicated by Professor 

 T. G. BONNET, D.Sc., F.R.S. Received June 16, 1890. 



(Abstract.) 



The nature of the evidence on which the accounts are founded is 

 stated, and the method of study described. If the disturbed area be 

 of small dimensions, and if its boundary be approximately circular 

 or slightly elliptical in form, it is assumed that the centre of the area 

 coincides very closely with the epicentrum of the earthquake. During 

 the year 1889 there were at least five earthquakes whose epicentra 

 were situated within the area of the British Islands. 



1. Edinburgh Earthquakes, January 18. (a.) First shock about 

 4 h. 10 m. Intensity (according to the Rossi- Forel scale, of which a 

 translation is given) about V. Very little is kuown about this 

 shock. 



(6.) Second shock, 6 h. 53 m. Intensity VI. The disturbed area 

 is slightly elliptical in form, being 30 miles long from north to south 

 and 26^ miles broad from east to west ; area about 620 square miles. 

 In most places the shock consisted of a single vibration. The charac- 

 teristic earthquake-sounds were beard in many places, and these places 

 are confined to an area which is neither coextensive nor concentric with 

 the disturbed area. The epicentrum is at a point about 3 miles VV. 

 42 S. of Balerno, and the centre of the sound-area about 2 miles to 

 the south or south-east of this point. The earthquake was probably 



