56 H. I. JENSEN. 



T then gives us the period in which to place the earthquake 

 or eruption, namely its distance from the minimum 

 ahead in terms of the interval between the two minima 

 in which it occurred. 



Mr. Espin found it a difficult matter to reduce his earth- 

 quakes and eruptions exactly, 



(1) because of the impossibility of giving the sunspot 



maxima or minima correctly to the decimal of a 

 year ; 



(2) because the records of eruptions are very imperfect. 



Mr. Espin also calculated earthquake frequency for 

 perigee, using m for the period of the moon's perigee. The 

 results which he obtains do not seem to bear out the views 

 advanced by Sir Norman Lockyer and independently by 

 myself. On the other hand tney seem to indicate a relation 

 between earthquakes and perigee. 



Mr. Espin's tables and curves seem to indicate a violent 

 paroxysmal outburst of volcanic and seismic energy at 

 sunspot minima, but no regular gradation from a maximum 

 to a minimum. Being interested in Mr. Espin's method of 

 reducing eruptions, I applied it to those eruptions and 

 earthquakes tabulated in my last paper. 



[These had been impartially taken out of standard text books, 

 such as Milne's "Earthquakes," Judd's "Volcanoes," and Lap- 

 parent's "Traite de Geologic, " partly because of the tediousness of 

 wading through the numberless magazines in which original 

 accounts are published, partly because it was the fairest way of 

 getting a representative collection of great earthquakes.] 



In working out the earthquake frequency by Mr. Espin's 

 method, I was hampered, as he, by the impossibility of 

 getting sunspot minima fixed to a decimal of a year, and 

 the impossibility with the books at my disposal of getting 

 exact dates for all the earthquakes. However, the result 



