TWENTY-SEVENTH ANNUAL MEETING. 237 



nuity of the coal seam is interrupted by a "trouble"— not like a trap dike 

 common in some coal regions, which is igneous rock protruded from below, 

 but this trouble is a broken mass of stratified rocks apparently dropped in 

 from above. After the trouble is passed through the coal seam is continuous 

 beyond, but rises to its former level. It was probably some seismic action 

 that opened a gap and let the upper strata fall in, but the gap was closed 

 before any great fracture had occurred at the surface. Only a sag took 

 place there, represented by what we now notice only as a comparatively slight 

 change of dip. And yet there may be more change, even fracture, near the 

 surface than we can discover, as the heavy cap of loess hides the bed-rock 

 all through the northern part of the city. 



There also appears to be a slight difference in the level of some strata on 

 both sides of Five Mile creek, but this I could only be sure oi by actual level- 

 ing. It is, however, probable that all watercourses more or less corre- 

 spond to the breaks or changes in the direction of the dip of strata. 



At the south side of Three Mile between Second and Third streets, and also 

 at the rock expose, south of the railway yard, it is seen that the rock dips 

 to the west. This westerly dip, combined with the northerly, gives a gen- 

 eral west by north dip which, with some exceptions, carries down the various 

 strata out of sight as we go away from the river, and others come in on the 

 top. This is true probably for the whole thickness of the coal measures. 

 The westerly dip is well illustrated by the position of the coal at Brighton, 

 as compared with that at Lansing. The distance between the two shafts is 

 2^/4 miles, almost due west. The coal at Lansing is 714 feet deep; at Brighton 

 it is 811 feet. The difference of level of the tops of the two shafts, as de- 

 termined by the railway survey, is G7 feet 9 inches, which leaves a depth of 

 291/4 feet to be accounted for by the dip beiween the two mines. This gives 

 a westerly dip of 13 feet per mile for the main coal. As the dimension 

 rock is 29% feet lower at Brighton than at Lansing, this practically gives the 

 same dip at the surface. 



The northerly dip of the district is seen in the difference above sea level 

 of the dimension rock and the Leavenworth coal vein at the penitentiary 

 and the Leavenworth Coal Company's shaft: 



Elevation Elevation 

 Penitentiary Leavenworth 



shaft. Coal Oo. Difference. 



Top of shaft 828.0 feet. 810.0 feet. 18.0 feet. 



Dimension rock . . . 774.9 feet. 776.9 feet. 



Vein coal 116.6 feet. 103.5 feet. 13.1 feet. 



This gives a dip at the dimension rock which is near the surface of only 

 a foot and a half and the vein coal of two feet four inches per mile. The 

 two mines are five and one-half miles apart, and the more northerly one is 

 nearly a mile further west than the other. There are local dips in the two 

 mines which lie between which exceed this amount, but they recover them- 

 selves in short distances. 



That this northerly dip is changed into a northerly rise north of the water- 

 works has already been noted. The dip westerly is, however, more con- 

 tinuous, though there are local easterly dips in several of the mines. 



The westerly dip carries all strata of the eastern part of the county down- 

 w^ards considerably in a few miles, so that in the valley of Little Stranger 

 and Salt creek none of the strata of our lower dimension rock series are 

 I'isible there, and the sandstones and shales that lie high up on the west of 

 Pilot Knob ridge are found in the bottom of the A'alley. Some of the car- 



