69 



at the negative pole will be found propelled as they are formed 

 toward the opposite pole. 



Granting these mutations in the southern hemisphere, it may 

 be said that they cannot have been going on during the last 

 thousand years in the northern hemisphere, otherwise they would 

 have been detected by astronomers, as the latitudes of places 

 must have varied. 



Let us examine what were the actual appearances of the is- 

 lands and continents, with their respective positions in the time 

 of Ptolemy. In comparing Ptolemy's observations with the 

 present we recognize great discordance. Even at the beginning 

 of the last century the position of places could not be depended 

 upon within 20 minutes. Let us suppose that the position of a 

 place was known a hundred years ago, and that it was situated 

 exactly in the equator ; in comparing the same point at distant 

 intervals of time with the same celestial objects, we find a dif- 

 ference amounting to a measurable quantity; and this difference 

 is proved by astronomical observations to be in one direction. 

 Consequently, in order to denote the latitude, or rather to pre- 

 serve it in the same relative spot, the position of the celestial 

 objects must be altered. This change is called the precession of 

 the equinoxes. To account for this movement it has been as- 

 sumed that the axis of the globe is continually altering its rela- 

 tive angular position in space, which apparent movement during 

 the historic period has been northward. The amount of this 

 motion, by which the equinox appears to travel, is 50 seconds 

 per annum, producing a change along the meridian of about 

 nineteen seconds. This relative change destroys, in the lapse of 

 a moderate number of years, the arrangement of the catalogues 

 of stars, and makes it necessary to reconstruct them. Since the 

 formation of the earliest catalogues on record the place of the 

 equinox has retrograded about 30 degrees. 



When the above hypothesis of the precession was propounded, 

 the earth's surface was considered as a fixed and immoveable 

 mass. So little was known of the phenomena of geology, mag- 

 netism, &c, that they were not consulted ; hence a change of 

 the whole globe appeared necessary to account for the observed 

 variation. The cause of such a movement has been attempted to 

 be explained by the assumed geometrical forces. It would be 



