THE AUTHOR'S THEORY OF THE TIDES 171 



at its present stage, especially noticeable and rapid. In 

 short, its peculiarities of motion are owing to the gradual 

 rounding of its orbit, the effects naturally dwindling 

 as the process of approximation to perfect balance pro- 

 gresses. As for the contraction of the comet 's head on 

 approaching perihelion, this is obviously due to nothing 

 else than the columnifying of the fused cometary nucleus 

 by the sun's differential attraction a phenomenon of 

 equilibrism pure and simple. 



LATITUDE VARIATIONS 



About the year 1890 astronomers began the investi- 

 gation of a unique phenomenon. This consists in the 

 circumstance that the latitudes of every place on the 

 earth's surface vary slightly from day to day the year 

 through, though they always return periodically to what 

 may be termed their home parallel much as the sun 

 crosses and recrosses the equator. In more graphic 

 language, the earth seems to wabble on its axis as though 

 that were a material axle and had worn itself thin in its 

 bearing, giving room for play. To illustrate: Let A 

 be a point on a given parallel and B another point on the 

 same parallel, but 180 distant in longitude; then when 

 observation shows the latitude of A to be slightly above 

 the parallel on which normally it belongs, the latitude 

 of B on that same day will be found just the same dis- 

 tance below, and vice versa. To explain this phenomenon 

 a dozen hypotheses of various sorts have been advanced, 

 but, so far, none has attained the stage of demonstration. 

 However, all astronomers are a unit in believing that the 

 phenomenon can be due only to an actual shifting of the 

 earth's axis with reference to the crust. In this view I, 

 for one, do not concur. 



Doctor S. C. Chandler, the eminent American as- 

 tronomer, has ably and carefully analyzed the observa- 

 tional data and found that this movement of the pole can 

 be expressed by a formula containing two terms, one of 

 which varies between 85-1000 and 185-1000 of a second of 

 arc, covering a period of about 430 days, and the other 



