PALEOZOIC GROUP. 309 



been shattered and baked or glazed only at the edges of the clefts. Wherever 

 the Silurian strata, especially the later members, have certainly covered the 

 magma the breaks are like those which would be produced by sudden snap- 

 pings, and the subjacent strata in such cases have not been broken in the 

 same manner as in the cases previously cited. In the valley of Honey Creek, 

 Mason County, south of the Menard road, there are huge bowlders of the 

 granite once covered by alluvium, but now exposed by stream erosion; and 

 southwest of this, between Honey Creek and Little Bluff Creek, north of the 

 Junction City road, a large area is occupied by blocks and hills of the same 

 rocks. These occurrences and the immense deposits of white sand over 

 much of the area make it very probable that the granitic extrusion from the 

 earlier strata rose to a greater height than the protrusion of the same magma 

 beneath the Silurian strata. Such a condition of affairs is compatible with 

 the hypothesis here advanced, if not really essential to its support. 



The importance of this feature will be appreciated when the later granites 

 are considered. 



We have still to inquire what cause or set of causes could have been 

 responsible for the elevation of the southern border of our district after the 

 Hoover deposition and prior to the San Saba Epoch. From the observations 

 of Mr. Jermy upon the Pedernales River, in Blanco and Gillespie counties, 

 and from incidental notes sent in from time to time by different observers, it 

 is thought probable that a very extensive land area existed southward after 

 the Hoover Epoch until long after the beginning of the Cretaceous Period. 

 Perhaps there will be found in that direction some further clew to orographic 

 movements which faded out in our area; meanwhile, we can only report the 

 result as an oscillation involving subsidence northward and elevation south- 

 ward. But extensive discussion on the subject at this time would be prema- 

 ture, because much remains to be done in collecting facts for the study of 

 just such questions. 



6. THE NIAGARAN (UPPER SILURIAN) SYSTEM (Absent?). 



There is abundant evidence that the sea retreated along the northern coast 

 before the sedimentation of the next period, for no Niagaran deposits have 

 been found anywhere in Central Texas, unless we are wrong in accrediting 

 the San Saba series to the Silurian. The uplift which we have assigned to 

 Post- Silurian times may have been more effective in folding the strata north- 

 ward, and indeed there is some little ground for such assertion. Mr. Cum- 

 mins, of this survey, informs me that his observations strongly support this 

 view as regards later shore lines in that quarter. There must, then, have 

 been a very large area of dry land during the period of accumulation of the 

 Niagaran strata in New York and Canada, or else contemporaneous deposits 



