182 J. D. Dana on the Green Mountain Quartzite, 
fied quartzite, in which, under the lateral pressure, fractures 
were produced, and where, consequently, the successive move- 
\ iB ! 
JOINTS IN THE POUGHQUAG QUARTZITE. 
In a case of this kind only a force that was comparativel aire 
i 
process, if continued, might result in a universal obliteration of 
the bedding. : 
It should be noted that after a quartzite had been consolida- 
ted this obliteration of the bedding would be an impossibility, 
however powerful the forces at work. The sand beds must be 
eebly compacted, or the sands could not be shaken down and 
re-arranged into a series of vertical or nearly vertical beds. 
Hence the jointed structure, when connected with absence of 
tainly not after it. peek 
_ Again, the quartzites of different periods are almost identical 
m structure and mineral characters, so as to afford nothing by 
which they may safely be distinguished. In the same region 
all kinds often occur, frora the finest and hardest granular 
quartz to pebbly layers, and to conglomerates made of stones as 
large as cobble-stones, on one side, and to thin friable layers 02 | 
the other. The presence or absence of a pearly micaceous OF 
talcoid mineral in the layers is not a distinction of value: Z 
may be a pure quartz rock in one place, a0 
even look gneissoid in another. > iene 
€ conclusion of the whole matter is, that the age of eac 
quartzite outcrop must be determined by an examination of its 
special stratigraphical relations to the aligning rocks. 
I proceed now to an account of the quartzite of a few oe 
Mountain localities. The observations at the first two of the 
following localities, Canaan and Poughquag, were made 1n con 
Junction with Mr. James T. Gardner, an excellent stratigrapht 
Cal observer, and one of the corps of the Clarence King ur 
