Feb. 1901. Observations on Indiana Caves — Farrington. 265 



m 



m 



The most unique feature of this cave is the pool at its end, 

 excellently described by Blatchley.* 



The calcite crystals which line the walls of the pool are made up 

 of the unit rhombohedron r (1011) and the unit prism of the first 

 order m (1010). (Fig. 9.) The crystals have all grown in a direction 

 at right angles to the plane of their attachment. The prism is quite 

 short, and no crystals are doubly terminated. The crystals vary in 

 size from quite minute to those the size of an ordinary acorn. It is 

 noticeable that they increase in size toward the bottom of the pool. 



In order to determine whether it was 

 commonly true that crystals increased 

 in size toward the bottom of a solution, 

 with the assistance of Mr. H. W. 

 Nichols, I prepared solutions of a 

 number of salts, placed them in long 

 slender jars and then immersing strings 

 vertically, noted the quantity and size of 

 crystals deposited. In nearly every 

 case the deposit took a marked conical 

 form. The base of the cone and there- 

 fore the greatest amount of deposit was 

 at the lowest point in the solution. It 

 was also generally true that the size of 

 the crystals increased toward the bottom. The accompanying plate 

 (PI. XXXIII), showing strings of crystals obtained from solutions of 

 copper sulphate, lead chloride and nickel-alum, illustrates this. Such 

 results point to a greater concentration of solutions at the bottom, 

 a principle already established with regard to solutions in general by 

 Ludwig and Soret.f It may be worth while, however, to call atten- 

 tion to this illustration of the principle, and to the fact that the 

 size of crystals depends on the degree of concentration of the solution 

 no less than on the time given for their formation. 



In this part of the cave stalactites and stalagmites of the ordi- 

 nary type appear in close association with the crystal deposits just 

 described. The formations have a similar origin in that they are 

 both deposits of carbonate of lime from solution in water. They 

 differ only in the condition that in the making of stalactites and stal- 

 agmites the water was moving, while in the making of crystals it was 

 still. If I am correct in this conclusion the converse of the principle 



Fk;. 9— Calcite, Coan's Cave. 



*Op. cit.. p. 132. 



tBecker, Am. Jour. Sci., Vol. 153, pp. 21-40. 



