6o2 CHARLES R. VAN HISE 



In such branches the probable energies, agents, and processes which 

 produced the observed results were developed from a consideration of 

 the methods by which chemical and physical energy through the agents 

 available could have produced the results observed. For instance, the 

 development of the solar system occurred but once. During that 

 development the earth was formed, including the atmosphere, hydro- 

 sphere, and hthosphere. The process of differentiation was not 

 observed by man, cannot be repeated by him. The only method of 

 reaching a probable conclusion as to the manner of accomplishment 

 of the complex result is to consider in what possible ways physical 

 and chemical energy may have acted upon the enormous masses of 

 universe stuff out of which the earth was constructed, and to check 

 this reasoning by the attainable knowledge of what is now occurring 

 upon other heavenly bodies. 



The qualitative and quantitative stages of explanation. — The 

 task of explaining geology in terms of processes involving energy 

 and agent has two stages — the qualitative stage and the quantitative 

 stage. For most problems we have as yet been unable to go beyond 

 the qualitative stage. In the qualitative stage of a problem it is 

 shown that a cause is real. In this stage the question is not asked 

 as to how far the explanation applies; i. e., its quantitative importance. 

 Most geologists are content when they reach the qualitative stage. 

 A certain cause is determined to be real in the explanation of certain 

 phenomena. It is then usually assumed that this cause is the only 

 cause. For instance, it has been generally accepted that the loss 

 of heat by the earth results in decreased volume, and that such con- 

 densation is a cause for crustal deformation. Many geologists have 

 stopped at this point satisfied. They have not asked the question: 

 To what extent can loss of heat by the earth explain crustal deforma- 

 tion, and are there any other causes which can be assigned ? Some 

 years ago I listed a number of causes, each of which partly explains 

 deformation. In addition to secular cooling, they are as follows: 

 volcanism, cementation, change of oblateness of the earth, change 

 of pressure within the earth, change of physical condition of the 

 material of the earth, and loss of water and gas from the interior.^ 



I C. R. Van Hise, "Estimates andXauses of Crustal Shortening," Journal qf 

 Geology, Vol. VI (1898), pp. 10-64. 



