188 Prof. Hennessy on Terrestrial Climate as 



increase with the temperature of the heat-bearing oceanic cur- 

 rents. A group of islands situated in high latitudes, and sur- 

 rounded by currents possessing a high temperature^ while re- 

 ceiving but a small amount of heat from sunshine, should present 

 a series of closed isothermals, and, while their interiors would be 

 cold, their coasts might enjoy an extremely genial climate. 



5. If such conditions existed at former geological epochs, we 

 may fairly expect to find some evidence of their existence by com- 

 paring the characters of the organized beings by which the 

 interior and the coasts of such islands were inhabited. Such geo- 

 logists as have hitherto studied the diversities in structure of the 

 fossil remains which have come under their notice, appear to 

 have attended principally to the climatic influence of the eleva- 

 tion of the interior parts of such islands. Professor Ramsay*, in 

 his memoir on the denudation of Wales, after pointing out the 

 great elevation above the sea, which portions of that region had 

 formerly possessed, calls attention to the resulting varieties of 

 climate that nmst have prevailed. " If," he says, " the climate 

 of our latitudes, when the coasts were washed by the new red, 

 and liassie seas, were tropical, as is generally supposed, still, on 

 the heights indicated on the vertical sections, we have ample 

 space for tropical and temperate zones, each probably abound- 

 ing in its own appropriate forms of life. And here, in connec- 

 tion with this subject, it may be remarked that in Mr. Brodie's 

 recent work, ' A History of the Fossil Insects of the Second- 

 ary Rocks of England,' it has been stated that, with certain 

 exceptions, the minute size of the great mass of the insect re- 

 mains seems to indicate a very cold, or at all events a temperate 

 climate." 



This appeared to Professor Ramsay not to be in harmony with 

 the other fossil evidence, which proves that most of the creatures 

 whose remains are preserved in the strata of the secondary series 

 inhabited a tropical climate. If the interior temperature of the 

 land, whose inhabitants apparently existed under such different 

 conditions of climate, depended not only on the coordinate of 

 height above the sea, but also on that of distance from the coast 

 in the manner here described, a more complete explanation 

 would be afforded of these remarkable phsenomena. The disco- 

 very by ]Mr. Strickland, in the alluvial sand of Worcestershire, 

 of the bones of a hippopotamus, accompanied not only by the 

 bones of other mammalia, but by twenty-three species of fresh- 

 water and land shells, of which nineteen are existing British 

 species, seems to show that, even at a period so recent as that 

 of the deposit from which these remains were taken, remarkable 

 differences of climate may have existed over a comparatively 



* Memoiro of tlie Geological Survey of Great Britain, vol. i. p. 324. 



