,558 SECTION MECHANICS. 



We had, at the very beginning of these researches, expressed our 

 opinion, that the phenomena observed in glaciers are, in more than one 

 respect, due to the mechanical deformation of the ice which is subjected 

 to the action of the immense burdens which its plasticity allows it to 

 transmit in all directions. 



Quite recently we were called in to help M. Daubree in his work on 

 the schistosity of rocks. The experiments made on this subject do 

 not let the slightest doubt remain as to the ease with which the very 

 least relative motion, caused in any mass whatever, were it even abso- 

 lutely homogeneous, would bring about perfectly manifest sliding ten- 

 dencies. The best way to make this most perfectly obvious is to 

 scatter in the mass little spangles of mica, which range themselves in 

 a line as exactly as may be observed in the micaschists following the 

 very plan of each one of the relative motions. In this specimen, for 

 example, which is the result of the flow of a piece of clay earth, through 

 the aperture of a rectangular drawing-frame, not a spangle can be seen 

 in the transversal fractures, whilst they all show themselves perfectly 

 ranged, one after another, on the clefts which are easily produced 

 longitudinally by taking advantage of the schistosity which earth pre- 

 serves as distinctly after its desiccation as in the schists of the different 

 formations. 



On the other hand, the crushing of blocks of earth or of lead be- 

 tween compression moulds which allow the matter to escape in one 

 direction only, has given us strikingly true representations of the 

 straightening of certain strata, their convolutions with schistose 

 qualities that are distributed throughout the body, and finally real up- 

 heavings, of which the bends and the rents are equally satisfactory 

 imitations. 



We are therefore quite authorised in saying that the study of the 

 flow of solid bodies, has already thrown some light upon geological 

 phenomena, or more generally, upon the phenomena of inorganic 

 nature. The question is, whether this will likewise be the case, in the 

 future, with regard to organic phenomena. The matter, however, 

 cannot yet be investigated scientifically : we only know that vegetable 

 growth is carried on by the formation of cells which always arrange 

 themselves in groups according to a tubular order, that certain animal 

 developments, such as the horny tissue?, assume, during their growth, 



