Geological Papers. ' 77 



step farther. This greater inclination will cause during win- 

 ter a higher barometer than now, i. e., greater atmospheric 

 pressure over the high latitudes and a low barometer in the 

 tropics. In addition to this, the much heavier winter snowfall 

 will greatly increase the pressure in the high latitudes. In 

 summer, of course, the condition of things will be reversed. 

 It is evident, therefore, the the northern hemisphere will then 

 be enjoying a higher pressure, while the southern will be enjoy- 

 ing a lower one than now, and vice versa. Besides this, the 

 attractive power of the sun and also of the moon upon the 

 higher latitude regions of the earth will vary more between 

 summer and winter than at present. Now, Mr. Alexis Perry 

 has shown conclusively from the comparison of a tabulated 

 list of nearly all the earthquakes that have occurred in our 

 history : 



1. That earthquakes are a little more frequent when the 

 moon is on the meridian than when she in on the horizon. 



2. That they are a little more frequent at new and full 

 moon than at half moon. 



3. That they are a little more frequent when the moon is 

 nearest the earth than when she is farthest away. 



(See Le Conte's Elements of Geology, p. 139.) Also, Le 

 Conte says that by an extensive comparison of this same list 

 of earthquake occurrences with the seasons it has been shown 

 that earthquakes are more frequent in winter than in summer. 

 And furthermore, Professor Knott has shown (see Le Conte's 

 Elements, p. 139) that the earthquakes of the present time 

 are brought on for the most part by the change of excess of 

 pressure between summer and winter and between the equator 

 and the poles. It is conclusive, therefore, that if the present 

 changes of pressure betw^een summer and winter and between 

 the poles and the tropics, and the variation of the attractive 

 power of the moon upon the earth from full moon to full moon 

 again, and her variation of attraction in conjunction with the 

 sun's upon the middle latitudes and the polar regions from 

 summer in one hemisphere to summer in the other are the 

 main causes of the quaking of the earth's shrinking crust to- 

 day, this greater change of excess of pressure and of the sun's 

 attractive influence, and also of the moon's, from winter in one 

 hemisphere to winter in the other, will cause the earth's crust 

 to yield in all its weakest points, which Le Conte says is at or 



