364 EHREXFELD— JOINTING AS A FUNDAMENTAL FACTOR 



When, however, the much larger subject of the reduction of the 

 Hthosphere in general to a condition of something like equilibrium 

 is considered, these so-called linal products of " clays " on the one 

 hand and of "peneplains" on the other are seen to be not final at 

 all but are really the end products of a series of agents which are 

 more or less accidental or local. The second point then upon which 

 I wish to rest a case is that the degradation of the Hthosphere in- 

 cluding both the factors of weathering and erosion is something 

 which is not essentially atmospheric in its control but is rather some- 

 thing which is a fundamental feature of the hthosphere structure 

 itself ; and that all the agents of frost, surface drainage, glacial ac- 

 tion, chemical weathering or other surface or atmospheric agents 

 are by their nature essentially accidentals which do influence local 

 results but are not the controlling factors. If I may illustrate the 

 point by an appeal to some other framed structures besides the 

 Hthosphere such as the behavior of metals under stress, we may 

 make the comparison by considering the active life or coherency of 

 a pair of car wheels or axles. This active life is conditioned not 

 so much by nature of the particular train of which the wheels or 

 axles are a part but rather by the nature of the steel and also by the 

 fact that it is almost, if not quite, impossible to make masses of steel 

 which will be destitute of flaws which will become joints, or to make 

 a steel which will continue elastic. The fact that one wheel may 

 outlive the other twice over in active service is more a question of 

 time factor than it is of difference of the agent which produced the 

 final break ; the eventual cause of the break will in the vast majority 

 of cases be due to some inherent factor in the wheels themselves 

 rather than to a particular agent or a particular occasion or accident. 

 One of the great problems of metallurgy to-day is to produce a 

 steel without joints and it is also one of the problems of geologists 

 when they try to conceive of the Hthosphere without these same fun- 

 damental lines of weakness which we call joints ; almost the only 

 condition of the Hthosphere where we can hypothecate no jointings 

 is in a molten mass. 



This tendency of earth matter to arrange itself in definite lines 

 of weakness seems to become more striking the farther we investi- 

 gate the fundamental structure and the behavior of the Hthosphere 



