J. D. Dana on the Quartzite of Canaan, Ct. 185 
of metamorphism *had to reach it through the thick horizontal 
limestone formation; for the gneiss where much tilted is a 
firmer rock. In some places about Canaan it is decomposed to 
a depth of thirty or forty feet or more, and then resembles a 
fine-grained soft sandstone. 
The quartzite is for the most part the ordinary fine or 
coarse-grained hard quartz rock. The ledges indicated on the 
above map are more or less completely surrounded by lime- 
stone, so that you cannot get from one ledge to another without 
crossing a limestone interval, although the distance between is 
in no case over 400 yards, and in one but little over 100. The 
quartzite evidently underlies the limestone. 
The rock is very strongly and evenly jointed, and nearly 
vertically so, and the joints are generally the only divisional 
planes, or are far more distinct than any planes of bedding. 
= direction of the joints in the several ledges is N. 80° HE. to 
. 87° E. : 
There is an exception in ledge No. 5 to this remark with 
regard to the absence of planes of stratification. This ledge 
has a bluff front facing the northeast, thirty feet high, in which 
the bedding is displayed in great perfection. It is made dis- 
