H. Arctowski — About Climatical Variations. 315 



this volcanic dust could not be washed out from the atmos- 

 phere, and remained therefore in suspension long enough to be 

 spread out all around the world, by the western drift of the 

 general circulation. Recently, C. Gr. Abbot has shown that 

 the dust projected by the eruption of Mt. Katmai, on June 6 

 and 7, 1912, affected the solar constant determinations made by 

 him and Mr. Fowle in Algeria and on Mt. Wilson. 



However, the occasional presence of volcanic dust, produc- 

 ing a general haziness of the atmosphere, as in the case of the 

 Krakatoa and Katmai eruptions, in particular, is a very inade- 

 quate explanation of the formation of antipleionian depressions 

 of temperature. The consecutive curves prove it very well. 

 The antipleionian depressions, on the curves of tropical sta- 

 tions, reoccur more often than the eruptions producing atmos- 

 pheric haziness. Besides that, the sedepressions are not V- or 

 U-shaped discontinuities, marking interruptions on a continu- 

 ous curve, but are preceded and followed by crests. Now, the 

 presence of such crests could not be explained by the volcanic 

 dust lxypothesis. All this, supposing of course striking coinci- 

 dences between the depressions of the equatorial temperature 

 curves and the volcanic eruptions producing dust veils in the 

 higher layers of our atmosphere, which is only exceptionally 

 the case. 



The brachypleionian, the pleionian and the macropleionian 

 crests of the consecutive curves demonstrate therefore with 

 evidence the fact that more or less periodical changes of the 

 solar constant must be the real primary cause of the various 

 climatic variations. 



Considering the means of the solar constants, observed by 

 Abbot during the summer months of 1905, 1906, 1908, 1909 

 and 1910, and comparing the differences between the mean 

 values with the corresponding differences of temperature in 

 Arequipa, I arrived at the conclusion that a difference of 1° F. 

 corresponds to a change of 0*01 of the solar constant. 



If this is the case, the lowering of temperature required to 

 produce ice age conditions, on our earth surface, could easily 

 be explained by variations of solar activity, in a measure which 

 does not exceed the differences actually observed between the 

 individual values of the solar constant. 



Differences of 0*15 to 0*20 have been observed every year. 

 Such differences, if permanent during some centuries or thou- 

 sands of years, would produce the required differences of tem- 

 perature. 



Hastings-on-Hudson, December 27, 1913. 



