PHYSICAL CLIMATE. 515 



ceeded, after the interval of four periods, or 36 years, by 1658, whose severity lasted 

 through the following year. The same interval brings us to 1695, and five periods more 

 extend to 1740, a very famous cold year; three periods now come down to 1767, nine 

 years more to 1776, and eighteen years more to 1794, the cold continuing through 1795. 

 Of the hot years, it may be observed, that four periods of nine years extend from 1616 to 

 1652, and three such again to 1679. From 1701 to 1718, there was an interval of 17 

 years, or very nearly two periods, while three periods reach to 1745, another period to 

 ] 754, and one more falls on 1763 ; and from 1779 to 1788 there are just nine years." 



But if Europe has a somewhat milder climate now than a thousand years back, the 

 evidence is irresistible, of an age of very high temperature, corresponding to that of the 

 torrid zone, having once characterised the whole northern hemisphere. The fossil flora 

 of our coal deposits plainly indicate a tropical climate by their gigantic size ; and the 

 carboniferous formation occurs in Melville Island, a latitude within fifteen degrees of the 

 pole. The fossil corals in the arctic limestone show that its waters once supported 

 polypi analogous to those which are found in our warm equatorial seas. The remains of 

 the elephant are found on the very shores of the frozen ocean in North Siberia ; turtles, 

 tortoises, and large saurians occur abundantly in the European strata ; and skeletons of 

 genera now confined to the hot regions are common in rigorous wintry latitudes. The 

 transport of these remains from the equinoctial zone to the places of their present deposit 

 cannot be admitted, owing to the perfect state in which they have been preserved, the 

 leaves and most delicate parts of the tree-ferns being quite uninjured, which is plainly 

 inconsistent with the assumption of a slow drift of one or two thousand miles having 

 been undergone. They have undoubtedly flourished at or near the sites of their depo- 

 sition, where there must have been the elevated temperature requisite for their growth, 

 equal to that now enjoyed by the vigorous vegetation of equatorial districts. What has 

 produced this change of climate is a question which we cannot answer ; but as we have 

 evidence of a progressive increase of heat with the depth of mines, the high temperature 

 of the interior might not have left the external shell of the earth, when the mammoth 

 roamed on the plains of the north, the turtle inhabited its waters, and enormous arbo- 

 rescent ferns clothed its surface. 



Boiling Mud of Iceland. 



LL2 



