OF THE EARTH*S SURFACE. 145 



nitic mass could not be conceived to extend farther than it 

 now does from the middle, that the whole granitic surface must 

 not only have been buried in everlasting snow, but that the ex- 

 tent of this snow must have been three times that of the gra- 

 nite. Now there is every reason to suppose, since the tempe- 

 rature diminishes as the height increases, that within this up- 

 per third, the temperature has never, in the hottest day in sum- 

 mer, reached so high as 32° ; that is to say, that water has ne- 

 ver there existed in a liquid form. We cannot, then, conceive 

 any block, however small, to have been conveyed from thence 

 by means of water, acting by the usual diurnal laws, 



M. de Luc admits the reality of M, de Saussure's debacle, 

 and accounts for it in the same manner ; but he does not 

 ascribe to it, either in Germany or in the Alps, the transportation 

 of the granitic blocks, the presence of which he accounts for very 

 differently. He supposes that these blocks have nowhere migra- 

 ted along the surface, but have been ejected from below, at the 

 places where they now lie. This ejection he produces by a 

 very extraordinary hypothesis *, founded entirely on gratui- 

 tous suppositions, and which affords no plausible solution of 

 the difficulty, by which we might be tempted to adopt it. 



M. de Luc mentions a theory formed by Mr Wrede, a Pro- 

 fessor of Berlin, to account for the same blocks. He embraces 

 a belief which seems to have been in considerable favour, that 

 the level of the Baltic Sea has been sinking for ages past, and 

 he extends his belief of the same change taking place in the 



Vol. VII. T whole 



* He supposes, that below the firm crust of the earth, then lying horizontal- 

 ly at the bottom of the sea, a set of caverns once existed, filled with peculiar elas- 

 tic fluids. That at a certain period, this crust breaking to pieces, fell with great 

 violence into these caverns, and drove out the elastic fluids contained in them 

 with such impetuosity, that the blocks of granite under consideration, which then 

 constituted portions of the lower part of the crust, were forced upwards into the 

 air, and fell back into their present position. 



