1889.] THE DISPLACEMENT OF BEACH-LINES. 17 



thinks that both the sidereal day and the month have be- 

 come much longer, and that the distance of the Moon has in- 

 creased; that the obliquity of the ecliptic has diminished, and 

 that a large amount of internal heat has been generated by 

 the internal friction. According to his calculation, the sidereal 

 day was, 46,300,000 years ago, 15 h. 30 m. and the Moon's di- 

 stance equal to 46.8 times the terrestrial radius (compared with 

 60.4 times now). But 56,180,000 years ago the sidereal day 

 was only 6 h. 45 m. in length, and the Moon's distance only 9 

 times the terrestrial radius, and the duration of the month only 

 1.58 days ( T Vth of its present value). The internal heat pro- 

 duced by friction during 57,000,000 years would, if presented at 

 one time, be sufficient to raise the temperature of the whole 

 Earth to 1700° Fahrenheit. 1 



He concluded that the oblateness has steadily been dimi- 

 nished, Jhe polar regions must have been ever rising, and the equa- 

 torial ones falling, though, as the ocean followed these changes, 

 they might quite well have left no geological traces. 2 The tides 

 must have been very much more frequent and larger, and ac- 

 cordingly the rate of oceanic denudation much accelerated. The 

 more rapid alternation of day and night (57,000,000 years ago 

 the year contained according to D. 1300 days) would probably 

 lead to more sudden and violent storms, and the increased ro- 

 tation of the earth would augment the violence of the trade- 

 winds, which in their turn would affect oceanic currents." 



Tresca (Comptes Rendus 1864 p. 754; 1867 p. 809 and other 

 places) has shown that ice, lead, indeed even cast-iron, even at 

 ordinary temperatures, may be so greatly compressed that their 

 internal particles become displaced in relation to each other, 

 like the particles of a liquid. Iron in solid condition may, under 



to considerably retard the secular cooling. Lappannt has paid no heed to 

 this in the previously named Memoir on the Earth's contraction and cooling. 

 In a subsequent work D., however, assumes that the beach-lines would be 

 displaced owing to the lengthening of the sidereal day. (Nature, 2 Sept. 



