TRANSLATIONS AND NOTICES 



GEOLOGICAL MEMOIRS. 



On Limestones in Crystalline Schists *. 

 By B. CoTTA, of Freiberg. 



[Zeitschrift d. deutsch. geol. Gesellschaft, 1852, 4 Band, 1 Heft, p, 47-53.] 



The metamorphosis indicated in the foregoing observations by M. 

 Scheerer may, it appears to me, be followed up further than to the 

 mere local conditions of crystallization. The limestone has often 

 been softened (by heat), to a greater degree indeed than the rocks 

 enclosing it. In this softened condition it has then been squeezed 

 into the neighbouring fissured rocks, in an eruptive form, from out 

 of its original place of deposition, so that, besides regular beds, it now 

 sometimes forms also veins, ramifications, and block-like masses in 

 them, — it has disturbed their lamination or bedding, — and en- 

 closes fragments or separated laminae of these rocks. Would not a 

 like result happen if we were to arrange alternating layers of wax and 

 glass or lead and glass and subject them to heat and imequal pressure 

 in different directions, so that the wax and the lead would soften and 

 melt and the glass remain unmelted ? The softened or melted state 

 of the limestonewas then succeeded by a crystallo-granular consistency, 

 accompanied by the formation of substances at the line of junction of 

 the rock-masses, which chemistry may readily explain. In consider- 

 ing the subject in this view, we must take care not to regard the 

 granular limestone in the same light as the true pyrogenous eruptive 

 rocks that have been poured out like lava from the interior of the 

 earth. To exist in an eruptive form as the result of melting is evi- 

 dently quite different from being ejected from subterranean sources. 

 This view, which has been urged by C. Leonhard, I have before now 

 sought to establish in the case of the granular limestones of Miltitz f, 

 Schwarzenberg %, and Striegisthal § in Saxony, and also of Auerbach || 



* This paper has reference to M. Scheerer's paper, supra, page 4, and to M, 

 Delesse's paper on ' Limestone in Gneiss,' Annales des Mines, tome xx. 



t Jahi-b. f. Min. 1834, p. 319 ; and Geognostische Wanderungen, part 1. 



t Erlaut, d. geogn. Karte von Sachsen, part 2, p. 242. 



§ Jahrb. f. Min. 1851, p. 572. 



II Grundriss der Geog. u. Geolog. 1846, p. 304. 

 VOL. IX. — PART II. D 



