114 M. de Beaumont on the Glacier Theory, 



for we know that water at 0° (32'^ F.), in order to become 

 converted into ice at 0", must lose a quantity of heat capable 

 of raising the same quantity of water from 0° to 75° cent. 

 The phenomenon cannot be easily conceived, unless there exist 

 in the interior of the glacier a sort of magasine of cold : this 

 magazine of cold cannot be derived from the diurnal variations 

 of temperature ; the annual variations alone are capable of pro- 

 ducing it. During winter, the temperature of the surface of 

 the glacier is lowered to a great many degrees below 0", and 

 this low temperature penetrates, although with a gradual di- 

 minution, into the interior of the mass. The glacier splits up 

 in consequence of the contraction resulting from this cooling. 

 At first the fissures remain empty, and assist in the refrigera- 

 tion of glaciers by favouring the introduction of the cold ex- 

 ternal air ; but in spring, when the rays of the sun heat the 

 surface of the snow which covers the glacier, they restore it 

 first of all to 0° (32° F.), and then cause the production of 

 water at 0° which falls into the cooled and fissured glacier. 

 This water immediately becomes congealed by the disengage- 

 ment of the heat which tends to restore the glacier to 0°, and 

 the phenomenon continues until the entire mass of the cooled 

 glacier is restored to the temperature of 0°. 



Hence results a certain amount of expansion which may 

 contribute, without any doubt, to the movements of glaciers, 

 but which explains still more distinctly one of the most curious 

 of the glacier phenomena described by observers. It is, in 

 fact, because the glacier thus augments by intus-siisception, 

 while it melts at the surface, that the stones originally en- 

 veloped in its mass are constantly brought to the upper por- 

 tion, where the superficial liquefaction disengages them, as 

 has been proved during the last year by MM. Martins and 

 Bravais ; it is also on this account that the interior of glaciers 

 at last becomes formed of ice nearly pure, as has at all times 

 been remarked by the inhabitants of the Alps. 



Even the existence of glaciers formed really of ice, like those 

 of the Alps, thus results from the annual variations and not 

 from the diurnal variations of the temperature, and it is for 

 this reason that there are no glaciers, but only perpetual snows 

 under the equator, where there are only diurnal variations of 

 temperature. 



