On the Influence of the Gulf Stream. 299 



of the cold of the Glacial period, for which he proves it to be 

 entirely insufficient. Mr. Hopkins showed at the same time, that 

 more might be said in favour of a maximum than of a minimum tem- 

 perature acquired in this way, but yet that, if our sun were to 

 approach a star within the distance of the planet Neptune, a case in- 

 compatible with the continued existence of the solar system in its 

 present form, the stellar radiation would not send to the earth much 

 more than a thousandth part of the heat which she derives from the 

 sun. The inappreciable increase of temperature derivable from this 

 source renders the hypothesis untenable so long as his reasoning re- 

 mains unimpugned. 



'' In order to estimate fairly the changes which may have taken 

 place, we must consider the several conditions on which the climate 

 of a given locality is dependent, viz, : — 



1. Its altitude above the sea-level. 



2. Its geographical latitude. 



3. Its distribution of land- and sea-surfaces. 



4. Hygrometric condition of atmosphere, cloud-formation and 



rainfall. 



5. The currents of the air and sea. 



6. The internal heat of the globe. 



The effect of the latter, being at present valued at only —^ C, may 

 be neglected in questions relating to recent periods, although it 

 must, in all probability, have formed an important item at the time 

 of the more remote geological events." 



The distribution of land- and sea-surfaoes — the hj^grometric con- 

 dition of the atmosphere, cloud formation, and rainfall — and the 

 currents of the sea and air, have such an immediate and intimate 

 connexion with one another that they cannot be treated separately ; 

 and their important influence upon the Flora of the Polar regions 

 deserves to be specially noticed — the more so, as they have been 

 considered by Dr. Heer as inadequate to account for so widely dis- 

 tributed a flora in Miocene times. 



From our knowledge of Tertiary Plant-beds in other parts of the 

 world, and of the extremely limited areas which they cover, as com- 

 pared with the associated marine deposits (the Carboniferous period 

 alone excepted), it seems unnecessary to demand for the Miocene 

 Arctic Flora a large and continuous land-surface, or to assume that 

 the whole Polar region enjoyed a luxuriant Flora at the same time in 

 precisely similar latitudes. On the contrary, we have every reason 

 to assume the reverse to have been the case. 



Take, for example, two parallels of latitude at the present day. 

 Mr. J. F. Campbell (author of ''Frost and Fire") writes July 30, 

 1864, " Off Little Belle-isle, air 48°, water 40° ; icebergs in sight 

 when the temperature was taken, wind south. Passed near a small 

 berg which rose 40 feet out of water. It must have been 400 feet 

 thick and 1500 long. Passed many others of far larger size ; some 

 were guessed at 200 feet high, and were certainly 150 feet above 

 water." ^ This is in the same latitude as London ! 

 ^ A Short American Tramp, p. 66. 



