CALORIC. 449 



the State presents the same general laws, as already stated, 

 and characteristic features of the climate of the eastern side 

 of the continent. Through this portion of their range they 

 are embraced between the isothermal lines of 50 and 45. 

 At this point the lines correspond with the lines of latitude 

 of 39 40' and 42. 



By following these isothermal lines around the globe, 

 as we have already seen, we will discover, that after 

 leaving the Alleghany summits and making the transit 

 of the Atlantic plain, and leaving the continent to cross 

 the ocean, there is a great deflexion north approaching 

 the eastern shore or continent of Europe. It has been 

 suggested that the lines in the Atlantic Ocean are carried 

 north by the vast river of hot water, whose liberated caloric 

 modifies to so great an extent the rivers of air of the ocean 

 above. This flowing sea is the Gulf Stream rushing north 

 through the bed of the Atlantic from the boiling heats of 

 the tropics. It will be seen that the lines of latitude which 

 correspond with these isothermals are, on the west of Europe, 

 50 and 60 ; thus showing the difference of 10 to 18 of 

 latitude between the two continents. As a direct conclusion 

 from this, it is evident that this range of mountains through 

 the State of Pennsylvania has an extremely low mean an- 

 nual temperature, lower than any other corresponding lati- 

 tudinal point, with a few exceptions, on the surface of the 

 globe ; in other words, is cooler than any other correspond- 

 ing point on the earth. 



The range of the thermometer must not necessarily, from 

 this fact, exhibit the exaggerated extremes or excesses of 

 the special climates of the continent. There may be, in 

 uncultivated wilderness extents, some difference in the 

 thermometric changes from the same parallels of the lower 

 surfaces of cultivated districts, or spots of particular local 

 influences. Observation will prove this, no doubt, and 

 establish the places. The elevation of the mountain, and its 

 parallel collateral ridges above the level of the sea, gives 

 also a greater range of caloric depression. As there is 



38* 



