4 o MY LIFE 



contrary to what it ought to he, yet when, later, the matter 

 was clearlv explained, I at once saw where my error lay and 

 had no further difficulty. I will here mention one of these 

 smaller stumbling-blocks, which I know are to this day quite 

 impassable by large numbers of persons who arc interested in 

 physical science. It is the fact that degrees of latitude 

 increase in length from the equator to the pole, the only 

 explanation usually given being that this is due to the com- 

 pression at the poles, or in other words, of the polar 

 diameter being less than the equatorial. Now nine persons 

 out of ten (probably more) who know what a "degree' is, 

 and have an elementary knowledge of geometry, and perhaps 

 a much more than elementary knowledge of several other 

 sciences, could not explain offhand why this is so; while 

 many of them, meeting with the statement for the first time 

 and trying to understand it, would come to the conclusion 

 that it was a mistake — perhaps a printer's error, and that 

 degrees really decrease towards the pole. For they know that 

 a circle is divided into 360 parts, each being a degree, and 

 if you draw a circle round the earth, passing through the two 

 poles with a radius of half the equatorial diameter, and 

 divide it into 360 equal parts, each of those parts will be 

 a degree. But the earth's radius at the poles will be about 

 132 miles less than at the equator ; therefore the degrees will 

 be proportionately less, not more as stated. I possess a pam- 

 phlet addressed to the President of the Royal Astronomical 

 Society by a Mr. Gumpel, pointing this out, and asking them 

 to correct so important an error. But I presume he was 

 only laughed at, as what Professor de Morgan called a 

 " paradoxer," and the Americans a " crank," and I dare say 

 the poor man lived and died in the conviction that astron- 

 omers were ashamed to confess their error. Now the 

 essential point, rarely explained in popular books, is, that if 

 the earth were of exactly the same shape it is now, but did 

 not turn on its axis, then degrees of latitude at and near the 

 pole would really be shorter than those at and near the 

 equator; but the bulging out at the equator is caused by 

 the rotation, owing to centrifugal force diminishing the force 



