262 Field Columbian Museum — Geology, Vol. i. 



ing, in the lapse of years, some data on this point Mr. S. M. Stewart, 

 manager of the cave, kindly allowed, at my request, several stalac- 

 tites and one stalagmite to be marked by Mr. Claude Stroud, who 

 lives near the cave, and who, by keeping watch of their growth, can 

 note any variations which they undergo. It will be understood, how- 

 ever, that the rate of growth is so slow that it is not likely that before 

 the end of ten years at least any appreciable change will have taken 

 place. The record of the stalactites marked is as follows: 



No. 1 Near " Tower of Babel," Drops at intervals of 3V2 minutes. 

 No. 2 In "Queen's Palace," " " " " 45 seconds. 



No. 3 " " " il 216 times per minute. 



These are simple stalactite tubes. 



The stalagmite marked is in "Crystal Palace Gallery," and 

 receives eighteen drops a minute. 



SH1LOH CAVE. 



Eroded Stalactites. — The stalactite shown in Fig. 7, occurring 

 near the southern end of the cave, furnishes an interesting illustra- 

 tion of the fact that cave waters may vary in their action from forma- 

 tive to erosive, according to the quantity of carbonate of lime they 

 contain. Thus, in the case of the stalactite here represented, the 

 waters flowing over the limestone shelf to which it is attached had at 

 one time built it up to the general form shown. Later, however, 

 the character of the waters changed and they began to erode, as shown 

 by the pits on the surface, the very mass they had previously built 

 up. These processes of deposition and erosion are, of course, going 

 on side by side in nearly all limestone caves, but it is not often that 

 erosion follows so rapidly after deposition. Many smaller stalactites 

 in other parts of the cave show similar erosion. 



Leaf Stalactites. — Many of the stalactites of this cave are leaf- 

 like in their form so far as this may describe a broad, thin and 

 pointed shape. Often the appearance is that of a series of ovate 

 leaves folded along their midribs and hanging down from a project- 

 ing ledge. The "leaves" of one such projecting mass are nearly 

 six feet in length, and the weight of the mass must be several thou- 

 sand pounds. It is remarkable that such a weight can be sustained 



