The Sun 289 



they are far from being total, nor should it be inferred 

 that they occur at regular intervals any more than do the 

 sun-spots. It is to these solar backslidings that I at- 

 tribute the alternation of genial- and ice ages, for which 

 scientists have so long been groping for explanation in 

 vain; and to them do I also attribute, in chief measure, 

 the enormous alterations of continental levels ushered 

 in with the glacial epochs. Obviously, the sudden libera- 

 tion of a great store of high-temperature gases would 

 greatly reduce the sun's radiation for a long time to fol- 

 low, and centuries would probably pass before he re- 

 cuperated to normal, and still other centuries ere he 

 could succeed in dissolving away the glaciers accumulated 

 during his prolonged lapse. As for the changes of level, 

 these may easily have been due to the convulsive shak- 

 ings of the solar web. These would, as a matter of 

 course, precipitate earthquakes on a grand scale, frac- 

 turing the crust in a multitude of places; and through 

 the fissures thus created the imprisoned gases would 

 make haste to escape, thereby not only giving rise to 

 numerous volcanoes and much fouling of the atmosphere, 

 but incidentally letting down the previously distended 

 crust. Nor should we here neglect to take account of the 

 lateral stresses due to the gravitation of the land masses 

 toward the north pole, for it is just at such a time of 

 equilibristic readjustment as this that this lateral pres- 

 sure should make itself most felt and improve the oc- 

 casion by raising up the great mountain chains. 



The problem as to just how often these central ex- 

 plosions of the sun occur may find its answer in the re- 

 sponse geologists shall give to the question as to the 

 frequency of ice ages. If, in the absence of definite 

 knowledge, we assume the earth to be a billion years old 

 and the average interval between successive ice ages 100,- 

 000 years, there should have been, to date, 10,000 such 

 ages and 10,000 such cataclysmal explosions. It is very 

 doubtful, however, whether geology, on account of oblit- 

 erations of its records, can supply a surer answer to this 

 query than solar physics may more directly and speedily 

 yield. 



