-1859] WRITINGS OF JOSEPH HENRY. 75 



lei to the coast, meets the Pacific in the latitude of about 34°. 

 The portion of tliis curve along the coast of the Pacific shows 

 the remarkable fact that the summer temperature is nearly 

 the same from latitude 32° to 45°, or through a distance of 

 13 degrees, the whole having the same temperature as that 

 of 41° on the Atlantic coast. This curve also clearly ex- 

 hibits the great effect which the vicinity of the lakes has on 

 the temperature of summer. While the dark lines indicat- 

 ing the mean temperatures of 40° and 50° are not at all 

 aff'ected b}'^ their proximity to these large bodies of water, the 

 mean temperature of the summer is materially reduced. We 

 may here call attention to the fact that the dotted line, de- 

 noting the winter, suddenly bends up at the same place, in- 

 dicating an increase of temperature due to the vicinity of the 

 same reservoirs of water. The line of 80° commences near 

 Charleston, South Carolina, and extends rapidly upward 

 through the valley of the Mississippi, thereby indicating that 

 the temperature of summer in the interior, along this paral- 

 lel, is much higher than on the seaboard. The western por- 

 tion of this curve also exhibits great intensity of summer 

 heat in the mountain system, and a remarkable degree of 

 uniformity along the coast range of mountains parallel to the 

 Pacific. The short lines of 82°-5 and 85° denote a high tem- 

 perature of uniform intensity, extending to the north, and 

 indicate the great summer heat of the western plain. 



It will be seen, by examining the dotted lines, that the 

 temperature of winter in the middle of the Mississippi valley, 

 about the 95th meridian, is lower than on either the eastern 

 or western coast ; also, that the line of 30°, which is only two 

 degrees below freezing, starts at the east end of Long Island, 

 passes through Lake Erie, thence down to the 40th parallel, 

 in longitude about 91°, and thence rapidly rises to the north, 

 and leaves the United States at the 118th meridian. The 

 line of 40° of winter temperature commences at the mouth 

 of the Chesapeake, follows nearly the same general direction, 

 and meets the Pacific Ocean near Puget's Sound, indicating 

 the remarkable fact that this place and Norfolk, on the 

 Atlantic, have about the same winter temperature. The line 



