TRANSLATIONS AND NOTICES 



GEOLOGICAL MEMOIRS. 



On the Origin q/" Crystalline Limestones. 

 By Prof. A. Delesse. 



[Bullet. Soc. Geol. France, Deux. Ser. tome ix. pp. 133-138.] 



M, Delesse, having just previously reviewed the general cha- 

 racters and mineral contents of different crystalline limestones*, 

 commences this communication hy defining "metamorp hie limestone" 

 and "metamorphic rock" as a rock which has been subjected, at a 

 period posterior to its formation, to considerable modifications in its 

 physical or chemical properties. These modifications are brought 

 about by the development of divers minerals, by changes in its struc- 

 ture of aggregation, or in its structure of separation, as well as in its 

 chemical composition. The modifications in the physical properties 

 of the rock result from the action of heat, electricity, magnetism, 

 pressure, as well as of all the agents that can bring into play mole- 

 cular attraction and repulsion. The modifications in its chemical 

 properties arise from the introduction of new substances in the rock 

 by injection, sublimation, secretion, cementation, and especially by 

 infiltration. 



M. Delesse then observes, — it appears to me that the crystal- 

 line limestones should be considered metamorpJdc : though certainly 

 they are metamorphic to very different degrees ; still they have all 

 been subjected, since their deposition, to modifications in their che- 

 mical, or at least their physical, properties. There are, however, 

 some limestones that form an exception ; namely those which have 

 been deposited by chemical precipitation, and which were originally 

 crystalline : these are not to be confounded vvdth the metamorphic 

 crystalline limestones, nor do they contain the minerals characteristic 

 of the latter. 



The crystalline limestone of the gneiss of the Vosges, which, from 

 its mineralogical and geological characters, M. Delesse considers to 



[* Loc. cit. pp. 120-133. See also Papers by MM. Delesse, Cotta, and Sclieerer, 

 supra, pp. 4, 15 & 19, et ncq, — Transl.] 



VOL. IX. — PAKT 11. F 



