EAR 



in the northern. In the one the ocean : the land : : 7:5; and 

 other : I 13 : 12. 



If \\-e suppose the mean depth of the ocean to be two mile?, th 

 content will be 290,000,000 of cubic miles. 



Comparative superficial extent of the frigid, temperate, and 

 zones, taking the whole area of the globe as unity. (Lacroix. ) 



- , - . 



in thf 

 cubic 

 torrid 



The frigid zones occupy 



The temperate zones 

 The torrid zone 



~ 

 iuUP 



EARTH, density of. See Moiwtain, attraction of. 



EARTH, internal temperature of. (Encyc. Britt. Supp.J 



In descending below the surface of the earth, a considerable increase 

 of temperature is observed, as the following examples prove. 



At Gircmagny, in the Vosges, annual temperature at surface is 49<> ; 

 at 110 yards depth, 53. 6 j at 336 yards, 60. 8 ; at 472 yards, 74. G. 



In Saxony, in four of the deepest mines, annual temperature at sur- 

 face is 460. 4 ; at 170 to 200 yards depth, 54. 5 ; at 280 yards, 58 ; at 360 

 yards, 6->. 0. 



In the coal mine of Killing-worth, the deepest in Britain, annual tern- 

 perature at surface is 48 ; at 300 yards, 70 ; at 400 yards, 77. In seven 

 others of the deepest coal mines in Britain, a corresponding gradation 

 was observed. 



In these British mines, the increment of temperature is about 1 for 

 15 yards of descent. In the Vosges it is about 1 for 20 yards, and in 

 Saxoay 1 for 22 yards. Taking 20 yards as a mean, if the increase fol- 

 lows the same arithmetical ratio to a considerable depth, we should 

 find the temperature of the Bath waters (116) at 1320 yards below the 

 surface ; and that of boiling water at 3300 yards, or nearly two miles. 



EARTH, pressure of against walls. 'Gregory.) 



Let D A E F be the vertical section of a 

 wall, behind which is placed a bank or tor- 

 race of earth, of which a prism, whose sec- 

 tion is represented by D A G, would detach 

 itself and fall down, were it not prevented by 

 th* wall. Then A G is called the line ofrup. 

 twre, or the natural slope, or natural decli- 

 vity, In sandy or loose earth, the 

 10 



B F 



A E 



