AND ITS DISTRIBUTION. 35 



fiery currents, had its source in the early and generally felt 

 desire of discovering a common cause for a great and com- 

 plicated series of phsenomena. 



Yiewing the variety of conditions which the surface of 

 the earth presents in respect to the reception and absorption 

 of the solar rays, and to the facility with which heat radiates 

 from the eartli into space, as well as the great diversity in 

 the conduction of heat by reason of the various composition 

 and density of different rocks, it is not a little wonderful 

 that where observations have been made with care and under 

 favourable circumstances, such (generally speaking) accordant 

 results for the increase of temperature with increasing depth 

 should have been obtained in such different localities. Borings, 

 especially where they are filled with water rendered rather 

 thick and muddy by the presence of clay, and thus less 

 favourable to the generation of internal currents, and sup- 

 posing there to be few lateral openings from whence affluents 

 from cross-fissures at different heights could be received, 

 present the greatest certainty ; and on this account, as well 

 as on account of their great absolute depth, we will b^gin 

 with the two most remarkable Artesian Wells, that of 

 Grenelle at Paris, and of Neu-Salz\verk in the Oeynhausen 

 Soolbade, near Minden. I subjoin the most accurate deter- 

 minations at both. 



According to the measurements of Walferdin,( 33 ) to whose 

 ingenuity we are indebted for a variety of delicate apparatus 

 for determining temperatures at depths either of the sea or 

 of wells, the floor of the Abattoir du Puits de Grenelle is 

 36 m ,24 above the, sea. The highest level to which the 

 water of the spring ascends is 33 m ,33 higher. This total 

 height to which the water rises above the level of the sea 



n 2 



