ANNIVERSARY ADDRESS OF THE PRESIDENT. Iv 



If we take earthquakes for our guide, these tremors appear to 

 follow laws which apply to elastic solids, not undulating fluids, and 

 yet they presuppose a shock or displacement, such as a fluid support 

 for a solid crust might well account for. 



Mr. Mallet has completed the * Catalogue of Earthquakes,' on 

 which he has been so long engaged for the British Association. 

 Aided by his son, Prof. J. W. Mallet, he has brought this great work 

 from the earliest notices of history to the end of 1842. From 1843 

 the labours of M. Perrey, of Dijon, in the same field, may be con- 

 sulted with equal confidence in their accuracy. Both these authors 

 have increased the value of their work by appropriate discussions in 

 relation to time — by centuries, years, seasons, months, and days — as 

 had also been done with equal ability by Mr. David Milne. They 

 have considered earthquakes also in relation to their numerical dis- 

 tribution in geographical space, and in relation to the rate, extent, 

 and direction of the movement. In many of the tables which 

 are given by those authors to represent the numerical relations of 

 earthquakes to seasons of the year, we find a preponderance of the 

 three earlier and three later months over the six months from April 

 to September. 



This appears to be the case throughout Europe and Asia, and con- 

 spicuously so in all the northern parts. 



In a general Table compiled to illustrate this point by Mr. Mallet, 

 we find, from the fourth to the nineteenth century inclusive, the 

 following number of earthquakes in each month : — 



January 228 



Eebruary 189 



March 172 



April 147 



May 126 



June 131 



July 148 



August 147 



September 147 



October 176 



November 148 



December 202 



If these numbers be represented by ordinates at equal distances, 

 they will mark out an annual curve, whose maximum is in January, 

 and minimum towards the end of May. 



The number of earthquakes which occur in the 



first three and the last three months =589 and 526 



And in the six median months =404 and 442 



M. Perrey has found by analogous process of tabulation (using 

 also a formula of interpolation which includes the angular value of 

 the age of the moon) that — 



1. Earthquakes occur more frequently at the syzygies (new and 

 fuUmoon). 



