202 The Field of Geology— McGee. 



certain seaward slope determined by bottom slope, marine currents, 

 wave action, etc. Thus the mass of sediments is collectively in 

 the condition of the mass of snow upon a roof or upon a mountain 

 side, i. e., in a condition of potential instability or inequipotential- 

 ity. If the mass is stable in either case, it is because the friction 

 among the particles exceeds the attraction of gravitation upon the 

 particles; and it is obvious that if particle friction were reduced by 

 augmentation of temperature or by alteration of constitution, or if 

 the efficiency of gravitation were increased by addition to the mass, 

 the point of stability might be passed, when the mass would move 

 in the direction of slope. It is equally obvious that if an inequi- 

 potential mass expand, the resulting movement will not take place 

 equally in all directions but in the direction of least resistance, 

 which is that of the slope. Now every deposit of sediments fring- 

 ing the continents is in a condition of inequipotentiality, and any 

 movement due to rise of isogeotherms must take place in a single 

 direction; and the movement will not be limited to that due to ex- 

 pansion, since other factors co-operate. But under the classifica- 

 tion tabulated above, any such movements fall into the consequent 

 class, and hence the hypothesis utterly fails as an explanation of the 

 obscure antecedent deformation by which active geologic processes 

 were initiated early in the history of the earth, and by which these 

 processes have ever since been maintained. It cannot be too strong- 

 ly emphasized that without continents zones of deposition could 

 not be formed, and that continents could not have come into being 

 without antecedent deformation. The case is simple. Either (1) 

 the primeval earth was highly rugose and gradation and conse- 

 quent deformation have always been employed in reducing the ru- 

 gosity, or else (2) a general deforming force of unknown value ha& 

 always been in operation — either the earth is a clock once wound 

 up and ever since running down, or else it is a prime motor whose 

 mechanism may be obscure but whose energy is ever renewed 

 within itself. To the W3rking geologist, constrained by the inex- 

 orable logic of facts, there is but one choice between these alter- 

 natives — the primeval earth was less rugose than the present, and 

 diastatic movement has not declined with the ages; and the grander 

 earth movements are in progress to-day and apparently as active 

 as at any time in the past. 



Thus it appears (1) that while the problem of consequent dia- 

 static movement has been at least partially solved, no attempt has 



