ii6 



VERNON C. ALLISON 



EFFECT OF THE VARIOUS FACTORS UPON THE GROWTH 



Approxiinately equal rates of vertical growth are noted for drips 

 varying from 3 to 368 seconds, although the diameter increases 

 with the rate of drip. The variation in concentration is very 



largely taken care of by the sta- 

 lactite, especially in slower drips, 

 before the solution reaches the 

 stalagmite. 



Bopid gnn>/i»^ sta/actite 



Y 



■Stow grom'ng stalactite 



SPLASH CUP 



The cup at the top of some 

 stalagmites is a "splash cup." 

 Stalagmites Nos. i, 2, 3, and 5 

 have cups of practically the same 

 diameter, although of varying drip, 

 and are about 40 cm. below their 

 stalactites. The greater the dis- 

 tance of fall, the greater the 

 diameter of the "splash cup." 

 S3rmmetrical No, 4 has no cup on account of its greater concen- 

 tration of drip. The cup of symmetrical No. 2 is deep, while 

 the other cups are shallow; also its rate of drip is more rapid. 

 The depth of the "splash cup" is increased by high evaporation, 

 low concentration, and rapid drip. 



Fig. 14. — Diagrammatic outline of 

 method of growth of stalactites. 



THE MODE OF ORIGIN 



At the start, a stalagmite is limited to a circle bounded by the 

 splash of the drops hitting the floor. Good evaporation and rapid 

 drip cause the formation of a saucer at the limit of the circle. The 

 bottom of the saucer slowly rises as lime is deposited in it, and the 

 excess solution cascades down over the rim and down the sloping 

 sides of the stalagmite until such a diameter and convex surface 

 are realized that the resulting evaporation surface will be just 

 sufficient to evaporate the solution it receives. The stalagmite 

 will now continue to grow vertically in a symmetrical form unless 

 conditions change. 



