CHEMICAL WORK OF WATER 175 



tion. Reduction or deoxidation may also go on at times, and so 

 may decarbonation and silication. Solution is less characteristic 

 than in the belt of weathering, while deposition becomes of the 

 greatest significance. Flydration and carbonation are important re- 

 actions, but oxidation is confined to the upper layers. 



Solution. This is most active in the belt of weathering. Lime- 

 stone, gypsum, and salt beds are dissolved by the underground 

 water, with the production of caverns sometimes of very limited 

 duration. The rate of solution may be estimated from the amount 

 of dissolved matter discharged by the springs of a given region, and 

 some data are available for this determination. Thus the warm 

 springs of Bath, England (mean temperature of 120° F.), discharge 

 annually a quantity of dissolved sulphates of calcium and sodium, 

 and chlorides of sodium and magnesium, sufficient to make a scjuarc 

 column of mineral matter 9 feet in diameter and 140 feet high 

 (Ramsay, quoted by Geikie-io: 477). The St. Lawrence spring at 

 Loueche, Switzerland, discharges every year 1,620 cubic meters 

 (2,127 cubic yards) of dissolved sulphate of lime, which is equiv- 

 alent to lowering a bed of gypsum one square kilometer (0.3861 

 square miles) in extent, more than 16 decimeters (upward of 5 

 feet) in a century (Reclus; Geikie-io: 477). It is estimated 

 that the Solnhofen limestone is reduced i meter in thickness in 

 72,000 years (Pfaff), and that of the Nittany Valley i meter in 30,- 

 000 years (Ewing-6: ji). T. Mellard Reade has calculated that 

 throughout the entire globe there is removed annually in solution 

 96 tons (about 86 metric tons or tonneaux) of material per square 

 mile, divided as follows : Calcium carbonate, 50 tons (45 ton- 

 neaux) ; calcium sulphate, 20 tons (18 tonneaux) ; sodium chloride, 

 8 tons (7.2 tonneaux) ; silica, 7 tons (6.3 tonneaux) ; alkaline car- 

 bonates, and sulphates, 6 tons (5.4 tonneaux) ; magnesium car- 

 bonate, 4 tons (3.6 tonneaux) ; oxide of iron, i ton (0.9 tonneaux) 

 (quoted by Van Hise-41 : 486). 



The rate of solution is strongly influenced by the temperature of 

 the solvent. "At temperatures above 100° C, and especially above 

 185° C, the activity of water may increase to an amazing degree." 

 (Van Hise-41 : 7p.) It thus follows that solvent action of water is 

 greater at the equator than in the arctic regions, where it is prac- 

 tically at a standstill when the temperature is below 0° C. Solution 

 at any temperature goes on until saturation is reached, which is 

 much sooner at high than at low temperatures. 



Through continued solution extensive underground channels and 

 grottos are produced within the upper zone of the earth's crust in 

 limestone regions. The presence of these is marked on the surface 



