36 INTERNAL HEAT OF THE EARTH, 



(69 m ,57) is in absolute elevation about 60 metres lower 

 than the out-cropping of the green-sand stratum in the 

 hills near Lusigny, south-east of Paris, to the infiltrations 

 of which the ascent of the water in the Artesian "Well of 

 Grenelle is ascribed. The water was reached by the boring 

 at a depth of 547 m (1683 Paris, or 1794 English, feet) below 

 the floor of the Abattoir, or 1675 English feet below the level 

 of the sea : the whole ascent of the water, therefore, is 

 1903 English feet. The temperature of the spring is 

 27'75 Cent. (81*95 Fahr.) The increase of temperature 

 is in this case 1 of the Centigrade thermometer for every 

 99 k Paris feet, or 1 of Fahr. for 58'9 English feet. 



The height at which the boring commenced at Neu- 

 Salzwerk, near Eehme, is 218 Paris feet above the level of 

 the sea (i. e. above the Pegel at Amsterdam), and it reached 

 an absolute depth of 2144 Paris feet below the point at 

 which the work began. The Sool-spring, therefore, which 

 comes out impregnated with much carbonic acid, is 1926 

 French, or 2053 English, feet below the level of the sea ; a re- 

 lative depth the greatest perhaps which has ever been reached 

 by man. Its temperature is 32'8 Cent., or 91'04 Fahr.; 

 and as the mean annual temperature of the air at Neu- 

 Salzwerk is about 9'6Cent., or 49'28 Fahr., we may infer 

 an increase of temperature of 1 Cent, for 92'4 Paris, or 98'5 

 English, feet, or of 1 Fahr. for 54'72 English feet. 



The boring of the well of Neu-Salzwerk,( 34 ) compared 

 with that of Grenelle, has a greater absolute depth of 461 

 French feet ; a greater relative depth below the level of the 

 sea of 354 French, or 377 English, feet,; and the tempera- 

 ture of its water is 5'l Cent., or 9'18 Fahr., higher. 

 The increase of temperature is therefore nearly T 'T 



