W. A. Norton on Molecular Physics. 65 
the history of the earth, when it was still in the process of con- 
densation, and its period of rotation was much longer than at 
present. It will readily be seen that at every epoch, during this 
‘ansition period, in which the period of rotation was the { part 
of the tropical year, n being an even number, the same region 
of the earth’s surface would, at the close of each successive year, 
» for a considerable interval of time, about the autumnal equi- 
to be reénforced by the new currents.’ The systems of currents 
thus originating, at such successive epochs, would not, in general, 
intensity, which would be in the highest degree improbable. 
Nee if the shifting movements of the different s rents 
ere unequ: | e lay 
88es, to bring them all into coincidence, or to consolidate them 
investigations into the magnetic state of the earth, we may con- 
clude that the earth has actually reached this period of its mag- 
toxes; in explanation of this see pp. 69,72. cnepe 
se 9 | | 
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