Curiosities of Science. 145 



subside most, and the hill will seem to be tilted in the opposite di- 

 rection. 



The fact is curious, and not less so are the results deduci- 

 ble from it. First, hills are higher at one season than another ; 

 a fact we might have supposed, but never could have ascer- 

 tained by measurement. Secondly, they are highest, not, as we 

 should have supposed, at the hottest season, but at the wettest. 

 Thirdly, it is from the different rates of expansion of different 

 rocks that this has been discovered. Fourthly, it is by converse 

 with the heavens that it has been made known to us. A va- 

 riation of probably half a second, or less, in the right ascension 

 of three or four stars, observed at different seasons, no doubt 

 revealed the fact to the sagacious astronomer of Armagh, and 

 even enabled him to divine its cause. 



Professor Hennessey observes in connection with this phenomenon, 

 that a very small change of ellipticity would suffice to lay bare or sub- 

 merge extensive tracts of the globe. If, for example, the mean ellip- 

 ticity of the ocean increased from ^ to | , the level of the sea would 

 be raised at the equator by about 228 feet, while under the parallel of 

 52 it would be depressed by 196 feet. Shallow seas and banks in the 

 latitudes of the British isles, and between them and the pole, would 

 thus be converted into dry land, while low-lying plains and islands near 

 the equator would be submerged. If similar phenomena occurred during 

 early periods of geological history, they would manifestly influence the 

 distribution of land and water during these periods ; and with such a 

 direction of the forces as that referred to, they would tend to increase 

 the proportion of land in the polar and temperate regions of the earth, 

 as compared with the equatorial regions during successive geological 

 epochs. Such maps as those published by Sir Charles Lyell on the dis- 

 tribution of land and water in Europe during the Tertiary period, and 

 those of M. Elie de Beaumont, contained in Beaudant's Geology, would, 

 if sufficiently extended, assist in verifying or disproving these views. 



THE OUTLINES OF CONTINENTS NOT FIXED. 



Continents (says M. Agassiz) are only a patchwork formed 

 by the emergence and subsidence of land. These processes are 

 still going on in various parts of the globe. Where the shores 

 of the continent are abrupt and high, the effect produced may 

 be slight, as in Norway and Sweden, where a gradual elevation 

 is going on without much alteration in their outlines. But if 

 the continent of North America were to be depressed 1000 feet, 

 nothing would remain of it except a few islands, and any ele- 

 vation would add vast tracts to its shores. 



The west of Asia, comprising Palestine and the country 

 about Ararat and the Caspian Sea, is below the level of the 

 ocean, and a rent in the mountain-chains by which it is sur- 

 rounded would transform it into a vast gulf. 



