THE GROWTH OF STALAGMITES AND STALACTITES 



113 



conditions are also about equal. A certain concentration evidently 

 is in equilibrium with the evaporation. When evaporation condi- 

 tions are lowered, the lime solution has a greater time interval 

 before precipitation after contact with the air. This allows the 

 solution, providing the drip is not too rapid, to be spread out by 

 capillary attraction before all the lime is precipitated. If the con- 

 centration is sufficiently high so that part of the lime remains 

 unprecipitated after the solution is spread out, this residual lime 

 is then precipitated over the enlarged diameter. The larger diam- 

 eter means the effect of lowered evaporation upon a drip of fairly 

 high concentration. 



Rapid vertical growth is favored by high air circulation, high 

 temperature, and high concentration, and is opposed by rapid 

 drip and high humidity. 



Large diameter is favored by low air circulation, low tempera- 

 ture, high concentration, and high humidity, and opposed by a 

 rapid drip (Fig. 14). 



Surface tension and capillarity greatly affect stalactitic growth, 

 but stalagmitic growth hardly at all on account of the larger surface 

 (necessary to evaporate the water received, which cannot drip 

 away as in the case of a stalactite) with the consequent 

 decrease of surface energy per sq. cm. Also, in the case, of stalag- 

 mites, gravity works against surface tension and is therefore mini- 

 mized. 



The more variables that can be ehminated, the greater the chance 

 for the solution of such a complex problem. The work on the rate 

 of growth will hereafter be confined to stalagmites which are affected 

 by rate of drip, air circulation, relative humidity, temperature, and 

 concentration, 



STALAGMITES 



TABLE II 



Experimental Mine Stalagmites Studied 



