270 EDWARD STEIDTMAN 



relation to the attitude of the bedding. Their origin is uncertain, 

 but a large proportion of them are probably tension joints controlled 

 by larger units of structure than Baraboo Range, 



The cleavage locally developed in the rocks of the Baraboo syn- 

 cline has been correlated with the folding of the range. 



The results of this investigation emphasize a principle which has 

 not often received adequate attention, that the secondary structures 

 are parts of larger structures, that these in turn are parts of still 

 larger structures, and that therefore the secondary structures may 

 be the key to the major structure. Description of joints, fractures, 

 cleavage, and faults, as so many isolated details, has value in the 

 interpretation of earth history, only when it leads to the correlation 

 of these structures with the major structures of a district. 



