28 J. D. Dana— Geological Relations of the 
than those of Dutchess County or Western Connecticut. This 
may be a consequence of their having been subjected to hotter 
silicated solutions in the metamorphic process, that is, to in- 
tenser metamorphic conditions, such as the coarse crystallization 
of the rocks would have required. But while there may b 
doubt as to the thinning in particular cases by this means, there 
is none as to the dissolving power of such hot silicated waters, 
and the tendency of their action to substitute silicates for 
the carbonate. Tremolite and light- -colored pyroxene, as long 
since suggested by the writer,’ are among the products that 
would naturally come from this action—dolomite tahlg a cal- 
ium-magnesium carbonate, and the minerals mentioned being 
silicates of the same bases. The fact that experiment has ob- 
tained pyroxene in crystals by heating ee the ingredients 
favors the conclusion. The tremolite of the more southern 
-portion of the Singsing limestone area often makes a gir 
envelope about portions of limestone, showing that it 
formed between fragments out of their material. If the dole 
mite is a ferriferous variety, the action might, in the same way, 
roduce green hornblende or actinolite, or green pyroxene. 
The only other magnesian silicate often present, and abund- 
ant in the adjoining schists, is Pere and this could have been 
roduced only where iron also s at hand. Chlorite might 
sae been formed under nearly he same conditions as biotite. 
Whatever the limestone beds lost through the action 2 the 
silicated solutions must have gone either to the making of 
these silicates or of other more soluble silicates ; for muscovite 
contains but one per cent or less of calcium or magnesium, and 
orthoclase none of either of these elements. 
lines of marshes iy such valleys, and many a lake ‘as been 
located by them. The beds of this soft rock stand nearly ver- 
tical, thus favoring the ex- 
1. cavation of deep channels. 
Zo 
Lise Mois 
7. 7 > 
CAROLS 
OLELON 
wah 
= oo) 
ao :, usually have one side high, 
> WY GY 4 WYGG44, Yee precipitous and rocky, and 
Cll AZ £L2 
the other gently sloping ; 
Be this is Bee due, in vr tn with the erosion, to the 
ag or dip of the beds. . The annexed figure illustrates the 
. D. Dana, on the Compson of Corals, and the Sher sing wear of the phos- 
ae, aluminates, silicates, and other minerals of crystalline limestones, by the 
orphic action of hot water, in this Journal, I, xlvii, 135, 1844. See also 
Bischof’s Lehrbuch Chem. Phys. Geol., 2nd edit., Engl. Transl., 1866, iii, 28. 
