THE TRAVELS OF THE UNDERGROUND WATER 185 



develops, and the deposit which is left thus takes the form of tiny 

 white rings at those points upon the crevice where there is the 

 easiest passage for the trickling water. To the outer surface of 

 these rings water will first adhere and then evaporate, as it will 

 also slowly ooze through the passage in the ring, but here without 

 evaporation until it reaches the lower surface. A pendant struc- 

 ture will, therefore, develop, growing outward in all directions by 

 the deposition of concentric layers which are thickest near the roof, 

 and downward into the form of a rock " icicle " through evapora- 

 tion of the water which collects near the tip. These pendant 

 sinter formations are known as stalactites and are thus formed of 

 concentric layers arranged like a series of nested cornucopias with 

 a perforation of nearly uniform caliber along the axis of the struc- 

 ture (Fig. 194). 



Formation of stalagmites. Wherever the water percolates 

 through the roof of the cavern so rapidly that it cannot entirely 

 evaporate upon the roof, a portion 

 falls to the floor, and, spattering as 

 it strikes, builds up a relatively 

 thick cone of sinter known as a 

 stalagmite, and this is accurately 

 centered beneath a stalactite upon 

 the roof. In proportion as the 

 cavern is high, the dropping water 

 is widely dispersed as it strikes the 

 floor, with the formation of a corre- FlG - 194. Diagrams to show the 



j- i XT.- i i T_I i. x i manner of formation of stalactites, 



spondmgly thick and blunt stalag- Stalagmite9 _ and sinter columns 



mite. As this rises by growth to- beneath parallel crevices upon the 

 Ward the roof, it often develops roofs of caverns (in part after von 



upon its summit a distinct crater- 

 like depression (Fig. 194, lower figure). When the process is 

 long continued, stalactites and stalagmites may grow together 

 to form columns which may be ranged with their neighbors 

 like the pipes of an organ, and like them they give out clear 

 tones when struck lightly with a mallet. At other times the 

 columns are joined to their neighbors to form hangings and dra- 

 peries of the most fantastic and beautiful design (Fig. 195). 



In remote antiquity limestone caverns afforded a refuge to many 

 species of predatory birds and animals as well as to our earliest 



