364 WILLIAM HERBERT HOBBS 



area comprising about 7,000 square miles in the southwestern part 

 of the state, and has also included areas surrounding the cities of 

 Madison and Milwaukee. In all cases the joints are in vertical 

 series, particularly well developed in the more compact limestones. 

 Mr. Harder's report upon the area will soon be published, and it is 

 possible here to refer to but a single area among those examined. 



For a considerable portion of the Richland Center Quadrangle 1 

 Mr. Harder's summary of the joint directions which he observed is 

 as follows: 



JOINT SERIES OCCURRING NEAR RICHLAND CENTER, WISCONSIN 



N. 5 W.-i N. and S.-7 N. 5° E.-19 



N. io°W.-2 N. i5°E.-5 



N. i2°W.-2 N. 2o°E.-s 



N. 15°W.-14 N. 22°E.- 2 



N. 20 W.-3 N. 25° E.-12 



N. 25°W.-16 N. 3 o°E.-2 



N. 28 W.-3 N. 35° E -35 



N. 3o°W.-5 N. 4 o°E.-i 



N. 35°W.-23 N. 45°E.-20 



N. 40° W.-i N. 46 E.-2 



N. 45°W.-14 N. 50 E.-6 



N. 50 W.-5 N. 52 E.-i 



N. 55°W.-23 N. 55°E.-9 



N. 6o°W.-9 N. 6o°E.-5 



N. 65°W.-9 N. 65° E.-l 2 



N. 7o°W.-5 N. 7o°E.-5 



N. 72°W.-2 N. 72°E.-3 



N. 75°W.-11 N. 75°E.-24 



N. 8o° W.-4 N. 8o° E.-2 



N. 8 2 °W.-2 N. 85°E.-9 

 N. 85 W.-S E. and W.-i 1 



It appears that in order of approximate numerical superiority the 

 more important joint directions of the Richland Center district are: 

 N. 35 E., N. 75 E., N. 55 W. (or N. 55°-65° W.), N. 85°-ao° E., 

 N. 35 W., N. 45 E., N. 5 E. (or N.-N. 5 E.), N. 25 W., N. 15° 

 W., and N. 45 W. The tendency of the five-degree interval to appear 

 is noticeable, and indicates that here, as elsewhere, the observations 

 of slightly curving planes become adjusted to the larger unit of the 



1 Surveyed, but not yet published. 



