E. 31. Kindle — Limestone Solution. 655 



sparingly branched, is a Chantransia or Pseudochantransia ; 

 probably imperfectly developed P. pygmcea (Kuetz.) nob. 



Ihr ganz ergebener 



F. Brand.' 



I think fifteen meters is the greatest depth recorded for this 

 species in Europe and no other Cladophora is known to go as 

 low as that ; so if 150 feet is correct for your plant, it is three 

 times as great a depth as before known. It probably occurs in 

 loose masses of considerable extent wherever it occurs at all." 



While the solution erosion to which these specimens have 

 been subjected is of the same general kind as that sometimes 

 observed on the face of limestone ledges near the surface 

 of the water, it is wholly different in degree. The writer has 

 never observed any examples of limestone solution in shallow 

 water which approached even remotely the deeply corroded 

 cavities shown by all specimens from the deep waters of Lake 

 Ontario. Ordinarily limestone slabs in shallow water show no 

 direct evidence of solution. The efficiency of wave action in 

 removing such evidence by attrition might be offered as an 

 explanation of the different results which follow limestone 

 solution in deep and shallow waters. But this explanation fails 

 because examples of such etching are wanting in small 

 protected inlets where wave action is absent just as they are 

 on exposed coasts. 



The explanation of the very markedly different results of water 

 acting as a solvent on limestone at considerable and at slight 

 depths rests upon certain chemical and biological facts which 

 will be briefly set forth. The importance of carbon dioxide 

 as the active factor in the solution of limestone is too familiar 

 to require more than mention. It is a familiar and generally 

 recognized fact that the solvent power of water on limestone 

 varies with the amount of carbonic acid in the water. The 

 effectiveness of water as a solvent of limestone will therefore 

 depend on the factors which tend to increase or decrease the 

 amount of this substance in it. These factors include the 

 varying degrees of solubility of the gas in water at different 

 temperatures and pressures together with the source of supply 

 of the gas. The first named factors represent well known data 

 of chemistry which may be stated thus : Water at 14° under 

 a pressure of one atmosphere dissolves its own volume of the 

 gas ; at the same temperature under two atmospheres two 

 volumes, and at three atmospheres three volumes, etc., of carbon 

 dioxide.* The amount which can be absorbed increases also 

 rapidly with the decrease of the temperature. The etched 

 limestone specimens under consideration came from a depth at 



* Richter's Textbook of Inorganic Chemistry, p. 230. 



