ii8 VERNON C. ALLISON 



again to about their previous magnitude, the stalagmite will exhibit 

 a "stool" effect instead of a "mushroom" effect. A decrease in 

 the drip or an increase in the evaporation conditions will cause 

 the stalagmite to take on a "needle" form while if the conditions 

 again return to about their original magnitude, the stalagmite 

 will acquire a "choked" effect. 



In the case of an abrupt slope between the large diameter and 

 the small diameter (lowered conditions of evaporation), a lowered 

 temperature is suspected because of its triple effect; decreasing the 

 air circulation if the cave is ventilated by the thermal syphon 

 method, reducing the vapor pressure of the lime solution, and 

 increasing the absolute humidity. Evidence of a change in the 

 air events of the cave will of course account for a change in the 

 conditions of evaporation. 



STALACTITIC CURTAINS 



Observations on the stalactitic curtains behind symmetrical 

 stalactites Nos. 2 and 3 Fig. 7 indicate that a slow drip, high concen- 

 tration curtain will increase in thickness ("diameter") about one- 

 fifth as rapidly as a stalagmite will grow vertically under corre- 

 sponding conditions, and a rapid drip, low concentration curtain will 

 increase in thickness about one-fortieth as fast as stalagmite will 

 grow vertically. 



SEASONAL INTERMITTENCY 



Present seasonal intermittency can be ascertained by observa- 

 tion, and the symmetry of the stalagmite shows whether or not the 

 present conditions held during its previous existence. If the 

 stalagmite is "dead," the face will show a sHght "needle" tendency, 

 together with a corrugated or "petticoated" columnar section, 

 similar to icicles,' if the drip has been seasonally intermittent. 



GROWTH INDICATIONS 



A sharply convex face means a rapidly growing stalagmite, and 

 a blunt face means a slowly growing stalagmite. The deeper the 

 "splash cup," the faster the drip, and the better the evaporation, 

 and the wider the "splash cup," the greater the distance of fall. 

 Absence of a "splash cup" means a high concentration. 



' Farrington, op. ciL, p. 263. 



