164 The American Geologist. September, 1894 
-i 
there is a continuous but gradual transition in color and crys- 
talline texture; or (I>) there is a brecciated zone. 
(a) In many localities where the white and blue limestones 
lie in close proximity, it is to be observed that the former has 
lost its most striking characteristics. It is no longer coarsely 
crystalline : its color is neither white nor yellowish white, but 
has rather a bluish tinge. The graphite, which, in the coarser 
rock, occurs in bright crystalline scales, appears rather as a 
dull earthy mineral, with occasional bright flecks. The rock 
has usually a pressed appearance, and in many instances a 
distinct slaty cleavage. At this stage the graphite, perhaps, 
would even yet suggest that the limestone should be classed 
with the crystalline series; but within a few feet these char- 
acters change, the rock becomes less and l'ess crystalline, the 
graphite loses the last trace of crystallization and shows as 
cloudy carbonaceous aggregations, and then comes the wholly- 
unchanged blue dolomite. This transition is to be seen in a 
score or more of localities; but to make sure that there was 
no possibility of error, the writer had a trench dug across the 
strike of the rocks showing a continuous exposure. The only 
result of this trench was to disclose more detail which served 
to verify the conclusions reached in other localities. 
(b) In another phase of the observed transition, as has al- 
ready been stated, the rocks are brecciated at the point where 
contact should be observed if they belonged to different hori- 
zons. Instead of the pressed appearance, with consequent de- 
velopment of slaty cleavage, one passes quite suddenly from 
the coarse white limestone to a zone of breccia. This is made 
up in places of practically unchanged, angular blue limestone 
fragments, with interstitial filling of coarsely crystalline, 
white, graphitic limestone. Breccias also occur in the midst 
of large white limestone belts ; and distinct fragments of 
limestone are frequently found which are less white, less crys- 
talline and less graphitic than the enclosing mass. If the 
white graphitic limestone is older than the blue, how can it 
contain fragments of it? 
•1. Dip "/it/ strike. There are many places which show ex- 
posures of both the blue and white limestones. Their dip is 
tli<- same, and also their strike. Instances may be found 
without number, and the details of many of them are given in 
