348 Mr. Weaver on F/oetz Formations. [Nov. 



occur in the greatest variety as to form, magnitude, and connec- 

 tion with each other ; but they all bear evidence of owing their 

 origin to the continued action of subterranean currents of water. 

 They usually form a connected series, extending several miles 

 under the earth, and filled with water to a certain level, which 

 either flows off from stage to stage to lower caverns, or finds an 

 outlet at the surface, constituting in some places lakes, or pools 

 of water. A remarkable connected chain of such caverns was 

 discovered near Wimmelburg, a few years since, by mining 

 operations, at the depth of 50 fathoms from the surface, proceed- 

 ing as far as explored 2100 feet upon the line of range, but pro- 

 bably to a much greater distance, if we may judge by the fractures 

 and sinkings of the earth, which appear at the surface. The 

 most spacious of these caverns are from 100 to 125 feet wide, 

 and from 70 to 84 feet high. 



These disruptions and sinkings of the strata, which mark the 

 course of the lower gypsum, differ much in size and form, resem- 

 bling a crater or vertical hole with abrupt naked walls, a circular 

 depression with sloping sides, or a long drawn winding concavity 

 in the form of a valley. Hollows of this description are found empty, 

 or filled with water, fresh or salt, and constantly or periodically 

 so. On the other hand, the sinkings which accompany also the 

 upper gypsum in the new red sandstone formation, occupy a more 

 extended space, with easier slopes and gentle routlines ; the 

 difference of which is to be found in the same action which ope- 

 rated on both formations, having been in the one case direct, 

 and in the other mediate. 



Salt springs usually accompany the cavernous gypsum ; and 

 in that of Bottendorf, examples are not wanting, although rare, 

 of the occurrence of rocksalt in it, in the form of small massive 

 pieces, or in thin veins, extending to the breadth of two fingers. 



Equivalents or Substitutes. 



As equivalents or substitutes of the preceding members of the 

 limestone formation, may be remarked in some tracts, a caver- 

 nous limestone, and a ferriferous limestone. 



The cavernous limestone (Hohlen-kalk) seems in general cha 

 racter to be most nearly related to rauhwacke, being also vesicu- 

 lar, and distinguished in like manner by great fissures and 

 dislocations of the strata. In the Hartz and the forest of Thurin- 

 gia, it is known by the name of rauh-kalk, where, though of local 

 occurrence, it extends over considerable districts, forming in 

 some parts cliffs of a grotesque appearance. In the former 

 country, it is described by M. Jordan as a yellowish-grey, 

 slightly fetid, limestone ; compact or granularly foliated, rough 

 to the touch, with numerous cavities, partly occupied by calca- 

 reous spar ; and free from organic remains. It prevails in the 

 southern and western parts of the Hartz, being in some parts 

 from 14 to 24 fathoms thick, and containing numerous caverns, 



