338 Dr, LeConte on a remarkable Exudation of Ice 



low the surface of the soil. We have already seen that the ice 

 does not extend below the surface when the pheenomenon is 

 well developed ; and it is well known that the degree of cold 

 necessary for freezing water is never observed in this latitude 

 at a greater depth than one or two inches. 



5. In seeking for a cause of the elevation of the fluid, the 

 first suggestion which presented itself to my mind was the 

 well-known and remarkable expansion which water undergoes 

 before congelation commences. In this we have a vera causa, 

 of sufficient universality and acting in the right direction, to 

 account for the phaenomenon, and yet perfectly consistent with 

 an \\x\YiOYiQX\t invariable concomitant cxTcum^Xfiuce, namely, the 

 unfrozen condition of the clay. But a little reflection very 

 soon convinced me that it must play a subordinate part in the 

 production of the phaenomenon, A simple calculation is suffi- 

 cient to place the inadequacy of this cause in a striking point 

 of view. According to the recent and very satisfactory ex- 

 periments of Joule and Playfair, the maximum density of water 

 is at 39°' 1 of Fahrenheit's scale (Phil. Mag. 3rd Series, 

 vol. XXX. p. W et seq. 1847). The very elaborate series of 

 experiments of Prof. Hallstrom show that the mean expansion 

 in volume between the point of maximum density and the 

 freezing-point (32° F.) is about 412 parts in 10,000,000 

 (Thomson On Heat, &c., p. 28. Lond. 1830). Hence it is 

 obvious, that if, by the unyielding character of the capillary 

 tubes, the whole of the increase of volume contributed to the 

 elongation of the column, the length of the column of water 

 requisite for furnishing 3 inches of ice through the operation 

 of this cause would be about 72,815 inches, or nearly 60S8 

 feet*. This reasoning is based upon the assumption, that the 

 temperature of the water at the orifice of the tube is at 32°, 

 while that at the other extremity of the column (viz. 6068 

 feet below the surface) is at 39°' I F. ; the only supposition 

 consistent with the absence of ice beneath. As the effects of 

 cold penetrate but a comparatively short distance below the 

 surface of the earth, the insufficiency of this cause is too appa- 

 rent to deserve further notice. 



Having thus shown the inadequacy of several presumed 

 causes to produce the remarkable phaenomena under consi- 

 deration, it is of course expected that we should offer some ex- 



* According to an extensive series of experiments made by M. Despretz, 

 the mean expansion of water between the points of maximum density and 

 freezing, is 4826 parts in 10,000,000. (Vide Pouillet's Elements de Physique 

 Experhnentale et de Meteorolopie, 5th edition, vol. i. p. 293. Paris, 1847.) 

 This makes the required length of column equ{\l %Q about 62,163 inches, 

 or 5180 feet. * 



