75 2 C.-R. VAN HISE 



mention. The first law is : All the elements and compounds of 

 nature are soluble to some extent in water. If water be placed 

 in contact with an hundred substances, it will hold some part 

 of every one of those substances in solution. It follows that 

 if, in the journey of underground water, it finds here and there 

 gold or silver or lead or zinc or iron, in quantity small or great, 

 those materials to some extent will be taken into solution. 

 The second law is the fundamental principle of chemical dynam- 

 ics, viz.; Chemical action is proportional to the active mass. To 

 illustrate, other things being equal, the greater the quantity of 

 a compound present, the greater the quantity which will be 

 taken into solution and deposited from solution. 



The materials will be likely to be taken into solution in large 

 measure during the descending course of the water ; and 

 deposited from solution in large measure during the ascending 

 course of the water. For this there are a number of reasons. 

 First, solution is likely to occur during descension because the con- 

 ditions are those of increasing temperature and pressure. It is 

 well known that increase of temperature greatly increases the 

 solvent power of water. In many cases a slight rise in tempera- 

 ture is sufficient to increase this activity in an amazing degree ; 

 in fact out of all proportion to the increase of temperature. 

 Deposition is likely to occur during ascension because the con- 

 ditions are those of decreasing temperature and pressure. 1 Sec- 

 ond, some substances are held in solution better than others. 

 Certain substances, such as quartz, may be deposited during the 

 downward course of the water, and a more soluble substance, 

 such as gold, silver, or some other substance, be dissolved 

 at the same time. Third, the larger openings, such as fissures, 

 are the trunk channels of water circulation. In them the 

 waters from different sources mingle ; and this to my mind is 

 the most important single factor — probably the dominant factor, 



1 The relations of temperature and pressure to solution and precipitation are much 

 more complicated than implied in the above general statement. For a more nearly- 

 exact expression of the facts see Some Principles Controlling the Deposition of Ores, 

 by C. R. Van Hise : Separate from Trans. Am. Inst. Min. Engineers, Vol. XXX, 1900, 

 PP- 38-43- 



