THE EARTH AND THE SUN 495 



scale would give it a value of 20. Again Jensen reckons 1855 at 17, 

 while Sayles put it in his lowest class which would give it a value of 

 only 7. The next year, on the other hand, is reckoned by Jensen at 

 only 4, and by Sayles at 14. Other years, such as 1873-4-5-6 and 22 

 others are given values of from 1 to 16 by Jensen, but are not men- 

 tioned by Sayles; while the latter gives an open circle to 1803, 1805, 

 1853, 1861, 1863 and 1885, although Jensen does not assign them a 

 value of even one. Other discrepancies might be mentioned. They 

 are natural, indeed unavoidable, in a subject where there is so much 

 opportunity for the personal equation, as well as for diverse authorities. 

 A man's estimate of the severity of an earthquake or eruption is sure 

 to depend largely upon the vividness of the account which he happens 

 to read. Hence the great value of having two independent sets of 

 data compiled for different purposes by men living at the antipodes, 

 New England and New South Wales. The discrepancy in the two sets 

 of data is an advantage because the one supplements the other, and 

 because where the original sources of information are so diverse, the 

 harmonious result derived from averages is highly remarkable. It 

 can not be the result of chance. 



Inspection of Fig. 1 shows that according to both Sayles and Jensen 

 periods of minimum sunspots are times of maximum seismic and vol- 

 canic activity; whereas at periods of maximum sunspots, telluric 

 activity almost ceases. There are certain glaring exceptions, such as 

 1883, or 1906 which does not appear in Fig. 1; but it should be noted 

 that in 1883 the sunspot maximum was only about two thirds as high 

 as the average. In order to estimate the true importance of such 

 exceptions, I have plotted the curves shown in Figs. 2-5, showing the 

 relative frequency and intensity of telluric activity in years of sun- 

 spot minima as compared with other years. Figs. 2 and 3 show the 

 frequency of years in which one or more notable earthquakes or erup- 

 tions — combined in the case of Sayles, separate in that of Jensen — 

 have occurred at the sun-spot minima and during the intervening years. 

 To illustrate concretely, it appears in Fig. 1 that out of fourteen years 

 of minima included in the period covered by the investigations of 

 Sayles, 11, or 79 per cent., have, according to him, been characterized 

 by notable earthquakes or eruptions. Out of the thirteen years im- 

 mediately preceding a minimum only 5, or 38 per cent., have had 

 noteworthy seismo-volcanic phenomena; out of those preceding a mini- 

 mum by two years, 6, or 46 per cent., and so on. Of course, the curve 

 soon comes to zero at either end, because, on an average, five or six years 

 before or after a minimum we come to a maximum separating one 

 wave of the sunspot curve from another. To illustrate again, 1867 was 

 a minimum year, and has a solid circle below the sun-spot curve and 



