NIAGARA LIMESTONE. 3gl 



liarities, it is thought best to depart from our usual order oi! descrii> 

 tion, so far as to consider, first, the local peculiarities of the formation, 

 after which we may, with more satisfaction, indulge in generalizations 

 and draw conclusions. 



Local details. At Racine, whence the formation takes its name, as exposed at the 

 rapids of Root river, it is a blue, gray or bufi', brittle dolomite, having a somewhat glassy 

 fracture, subcrystaUine structure in part, and earthy in part, and contains many geodic 

 cavities, filled with calcite and pyiite, and sometimes mammillary deposits. Its textm'e 

 is uneven, being sometimes granular and again brecciated, usually coarse and porous, 

 but sometimes fine and compact. It is frequently stained with iron oxide, and, in places, 

 is quite pyritiferous, especially in the fissures. The bedding is also irregular, but usually 

 rather heavy, ranging from five feet downwElrds. In the south quany at this point, be- 

 longing to Mr. florlick, there is a, small mound of highly porous blue rock, without vis- 

 ible bedding, fuU of fossils, from which it doubtless had its origin, after the manner of 

 reef formation. It is surrounded on all sides by bedded rook. The dip at this point is 

 varying in amount and direction, as shown by the following record of observations in 

 different parts of the three quarries near the rapids : 



EAST QUARRY. 



Dip 8°. Du-ection N. 47° W. 



Dip 7°. " N.40°W. 



Dipr. " N. 65°W. 



Dip33^'. " -. W.45° S. 



WEST QUARRY. 



Dip 5°. Direction N. 65° W. 



Dipl3^°. " N.irw. 



Dip 2°. " N. 30° W. 



Dipr. " N.63°W. 



NORTH QUARRY, WEST SIDE. 



Dip 0°. Direction 



Dipl°. ■' 3.80° E. 



NORTH QUARRY, BAST SIDE. 



Dip 0°. Direction 



Dipr. " N.30°E. 



It is understood, of com-se, that these measurements were made in different parts of 

 the quames, and on diff'erent layers, and they doubtless do not m all cases represent tho 

 true dip; i. e., the maximum inclination, as the exposure often did not render the 

 demonstration of this possible. But the general fact of uregularity is sufficienty sho-svn, 

 and it is to be noticed that the average dip is to the N. W., a dhection opposite to the 

 general dip of the formation. 



Fossils are very abundant, in the form of imperfect casts. At Vaughn's quarry, less 

 than two miles distant, the first six oi eight feet, as it hes in the beds, is deep yellow in 

 color, verging to orange and red on the one hand, and to pale buff on the other. Below 

 this the color varies from ashy-gray to grayish-blue. The upper layers are apparently 

 thinner bedded than those below, though this is probably only the effect of the elements. 

 The lower layers are heavier, but do not often exceed a foot in thickness. The beds are 

 but obscurely defined, so that it is difficult to trace a given onefor any considerable dis- 

 tance, or to ascertain the dip with any precision. There is an almost entire absence of 



