426 W. M. Fontaine—Primordial Strata of Virginia. 
belt. Stated briefly, they consist of two ledges of limestone, 
80 to 100 feet thick, enclosed in a vast mass of mica slate, and 
separated from each other by an interval of from two to three 
miles, principally occupied by the mica slates, in which occur 
two ledges of quartzite, each about 100 feet thick. This mode 
of occurrence indicates reduplication by folding. The dip is 
nearly vertical, while on each side the strata dip toward them. 
8. Prof. Rogers states that in certain parts of the quartzites of 
this series he saw enclosed fragments of mica slate. 4. Ata 
slate quarry in the rocks of this series, occurring in Bucking- 
ham Co., on the east of the Catoctin Mountains, Credner states 
that he found undoubted specimens of a cyathophylloid coral. 
He does not give a more particular description. He also states 
that they were badly preserved. I have not visited this quarry, 
but propor to doso. Should Credner not have been mistaken, 
his discovery would of course indicate the Silurian age of the 
slates of the quarry. 
Before closing this paper, I will add a few remarks on meta- 
morphism, suggested by ray studies of the Virginia rocks. 
Some writers on the subject attribute regional metamorphism 
mainly to three agencies, viz: 1. Increased heat and pressure, 
caused by thick deposits. 2. The saturation of the strata with 
moisture. 3. The change of motion into heat, which involves 
a considerable disturbance of the metamorphosed region. I have 
not observed that close connection between the first and third 
of the above-mentioned agents, and the degree of metamorphism 
in a given region, which should exist if these bear to each 
other the relation of cause and effect. In order to show this, 
I must compare the condition of the strata in certain parts of 
the State, which, in the amount of metamorphism poss y 
them, stand in strong contrast. For the purpose of this com- 
parison I shall call the belt of country lying between the 
western edge of the great valley of Virginia and the Blue 
Ridge Mountains, a portion of which is described in this paper, 
the Primordial belt. The region extending from the Blue Ridge 
eastward, and bounded by the northeast and southwest line given 
above, may be styled the Middle belt. On the east of this belt, 
and between it and the Tertiary strata which extend some dis- 
tance inland from the Atlantic, is a third belt, occupied by 
