30 



STRATIFIED ROCKS. 



Upper 



Wall-case 40. 



it abstracts from the air. Such part of the water as 

 percolates through rocks containing lime is thus enabled 

 to form a soluble bi-carbonate, and rising in springs or 

 dropping from the roofs of caverns, evaporation takes 

 place, and a portion of this mineral is deposited in the form 



of stalactites, stalagmites, and calcareous tuft 



$ 



A 



familiar illustration occurs in the stalactitic pendant 

 hanging like icicles, from the arches of almost every stone 



bridge. 



In the same manner stalagmites are formed by 

 the dropping and evaporation of calcareous water on the 

 floors of caverns, &c. and calcareous tufas are frequently 

 formed in the open air by the evaporation of the water 

 which flows over the surfaee from springs highly charged 

 with lime. The bones of many animals, mostly extinct 

 species, have been preserved in numerous caves in the lime- 

 stone rocks of Great Britain, partly through the agency of 

 stalagmitic crusts which cover them up, and protect them 

 from the air. ]S T os. 1 to 19 especially illustrate the formation 

 of stalactites and stalagmites. Tufas formed in the open air 

 frequently encrust mosses, grasses, leaves, stems of plants, 

 land and fresh-water shells, &c, which thus become fos- 

 silized before our eyes. (See Nos. 25 to 31.) 



Laminated and crystalline aggregrations of various sub- 

 stances are in an analagous manner frequently formed in 

 the interior of lodes, and other cavities. (See Nos. 18 and 

 24.) A. C. Eamsay. 



Wall-case 40. 



Sedimentary Rocks. 

 Arranged and described by H. W. Bristow. 



Some of the Specimens consist of nearly pure carbonate 

 of lime. Carbonate of lime consists of- 



Carbonic acid 

 Lime - 



- 44-00 



- 56-00 



100-00 



o 



f 





feec 



P 



iiP 





 geri 



3. 

 slid 



i 



*•», 



fron 



Ricl 



} 



the 

 ( 



1. 



kra 

 8, 



lead 



the in 



to ha 

 John 



of 



cai 



rese 

 10.. 



* 



re. 



11. 



Prod 



111 



o. 



