2 8o POPULAR LECTURES AND ADDRESSES. 



greater part of the twenty-four hours, and the 

 newly formed wood fibres are hence more perfectly 

 developed, they are much longer, present no signs 

 of striae, but are studded with discs of a more 

 highly organized structure than are usual in the 

 natural order to which this tree belongs.' 1 



" Another circumstance which shows that the 

 tree had grown where it was found is the fact 

 that in digging up the roots portions of the leaves 

 were obtained. It may also be mentioned that 

 near this place was found an old river channel cut 

 deeply into the rock, which at some remote period, 

 when the climate must have been less rigorous 

 than at present, had been occupied by a river of 

 considerable size." 



The theory set forth by Lycll in the celebrated 

 twelfth chapter of his Principles of Geology, 

 according to which variations of climate arc 

 explained by variations in the distribution of land 

 and sea, seems amply sufficient to account for 

 forests of such trees as now flourish in northern 



1 /'//// .',>// 7iV/w/ /;>;- 1885, )>:it!y }Si. '/'//, tasf OJ 



' ;Si. 



