374 
the most earnest attention to some of the very thoroughly 
ascertained facts of geology. We observe that Sir Charles Lyell 
says : “ Mr. [now Dr.] Bowerbank, in a valuable publication 
on the fossil fruits and seeds of the island of Sheppey, near 
London, has described no less than thirteen fruits of palms of 
the recent type Nipa, now only found in the Molucca and 
Philippine Islands, and in Bengal.” He says also, that “the 
teeth and bones of crocodiles and turtles ” are found here, 
with other relics of an unquestionably tropical character. 
Here then fairly occurs the question as to whether all these 
undoubtedly tropical productions and living creatures grew in 
the present latitude of London ; or have the relics of a truly 
tropical situation been transported northward by the removal 
of the strata in which they were entombed ? Certain minor 
causes might, perhaps, account adequately for a milder climate 
prevailing in England, or in its latitude, than even that which 
is produced by the Gulf-stream now. But it is impossible, 
apart from the vertical rays of a tropical sun, to account for 
the richest results of a tropical clime ; and the very richest are 
entombed in the London clay. Is it not evident that this clay 
was formed within the tropics, and that somehow it has been 
removed, until it lies in our northern latitude ? And is it not 
this removal alone that can account for the difference between 
its climatal character and that of the beds of sediment now 
forming in the Thames ? But if such is the account to be given 
of changes in climate, we must recast our ideas of the extinc- 
tion of species, and alter our views of what is called geological 
time. The shutting off of the warm waters of the great 
Atlantic current from our shores might bring a glacial period 
over Britain ; but as we know, the letting on of those waters 
would not give us the heat of Bengal. Ho raising or sinking 
of the surface, which could be conceived, could give us the 
effects of the direct radiance of a tropical sun without those 
rays themselves. But the removal of the abodes of tropical 
creatures from under tropical skies is abundantly sufficient 
to account for their extinction or emigration from the portion 
of the earth* s surface so removed; and it requires only, that 
we should be able to form some true idea of the time consumed 
in this removal, in order to our coming somewhat near the 
date of the extinctions and emigrations which the records of 
the rocks disclose. 
It is at this point that we are, as it were, compelled to look 
into current astronomy, where that science has been called in to 
account for changes on the surface of the earth. And here, 
too, we must distinguish between practical and physical 
science. Because astronomers predict, to the fraction of a 
