244 Proceedings of the Royal Physical Society. 
currence of analogous changes is expected by them in time 
to come The greater warmth that seems to have 
prevailed in some former periods of the world's history is not 
to be ascribed to a greater degree of heat in the globe itself, 
but to a different distribution of land and water. If we were 
to imagine all the land to be collected together in equatorial 
latitudes, and a few promontories only to project beyond the 
thirtieth parallel, would be undoubtedly to suppose an ex- 
treme result of geological change. But a mere approxima- 
tion to such a state of things would be sufficient to cause a 
general elevation of temperature. If there were no arctic 
lands to chill the temperature and freeze the sea ; if the ab- 
sorption of the sun's rays was in no region impeded, even in 
winter, by a covering of snow, the mean heat of the earth's 
crust would augment, the water of lakes and rivers would 
be warmer in winter, and never chilled in summer by melt- 
ing snow. A remarkable uniformity of climate would pre- 
vail amid the archipelagos of the temperate and polar 
oceans, where the tepid waters of equatorial currents would 
freely circulate. We might expect, in the summer of the 
great year, plants allied to genera now called tropical. 
Forms now confined to arctic and temperate regions would 
almost disappear ; coral reefs would be prolonged again 
beyond the arctic circles, and droves of turtle might begin 
again to wander through regions now tenanted by the walrus 
and seal." 
There are some parts of this hypothesis v^ith which we 
cannot concur. In the first place, we cannot suppose it 
possible that the tepid waters of equatorial currents would 
freely circulate, at a time when, according to Sir Charles' 
theory, the torrid zone was almost entirely occupied by 
land. The ^imount of water warmed by the sun,, and flow- 
ing to the higher latitudes, necessarily depends on the ex- 
tent of watery surface that is exposed to the influence of the 
solar beam. If the torrid zone were almost entirely covered 
with land, as he supposes it to have been in the period of 
the earth's highest temperature, there could not possibly 
have been any of those equatorial currents of which he 
speaks as warming the archipelagos of the northern ocean. 
