INTRODUCTION. 245 



his position for lack of public support in March, 1874.* Had Mr. Buckley's 

 work, befor,e and after this date, been of such a character as to entitle it to 

 much serious consideration, it would be improper to introduce Mr. Glenn's 

 unpublished work in this order, for no publication of it has as yet been made. 

 But we are fortunate in having access to the original manuscript of Glenn's 

 report, which accidentally came to light recently among the State arch- 

 ives. I Mr. Glenn's survey area comprised "the country for ten miles upon 

 both sides of the Colorado River, from the southeast corner of Burnet County 

 to the north line of San Saba County." His report, though brief, is a modest, 

 and, for the time, considering Indian depredations, etc., a very creditable 

 treatise upon the geology of the field traversed; for it must be remembered 

 that he was in the field only a few weeks. In the document referred to he 

 writes : 



The limited area worked over can best serve principally as an index for the future work, 

 and will not authorize definite conclusions except for that area. 



The principal disturbance which that section has been exposed to appears to be of the 

 Azoic Time, and is characterized by the disorder and confusion of the formations of that 

 time. The upturned, folded, and contorted conditiou of the rocks admits of no other conclu- 

 sion. 



With the appearance of the Paleozoic Time a period of tranquillity ensued, effected only 

 by gentle upheavals and subsidences, with conformable accumulation of strata; until the 

 Periods of the Potsdam sandstone, Trenton, and Hudson had passed, when there was evi- 

 dently a long rest in upheaved condition lasting through the Niagara, Salina, Lower Helder- 

 berg, Upper Helderberg, Hamilton, Chemung, Catskill, and Subcarboniferous Periods; when 

 subsidence again occurred, and the formation of the coal-bearing series began upon and 

 conformable to the Lower Silurian, upon which it rests. * * * 



There appeared a gradual diminution of the dip angle from the Silurian to where work 

 ceased in the Carboniferous; from an average of 15 degrees to 20 degrees near the Azoic to 

 an average of 3 degrees in upper part of San Saba County. Where the Carboniferous suc- 

 ceeds and lies conformable to the Silurian, the dip angle was 5 degrees. 



Generally the dip direction had direct relation to the Azoic. If to the northeast of the 

 Azoic, then northeast; if southeast, then southeast.:}: * * * 



The Azoic consists of the red granite principally intersected by numerous dykes of quartz 

 nearly vertical. Occasionally it is gneissoid; and, where the bisulphuret of iron exists 

 throughout it, the disintegation after exposure is rapid. 



* These facts appear (with some account of the work done along the eastern border of the 

 Central area in Blanco, Burnet, Llano, and San Saba counties) in a letter to Prof. Hill from 

 Mr. Glenn, published in the Bulletin of the United States Oeological Survey, No. 45, pp. 

 39, 40. 



f A Preliminary Report on the Oeology of the State of Texas. By John W. G-lenn, State 

 Geologist, 1874. Manuscript in possession of the Geological Survey of Texas, Austin, 1889. 



Jit is much to be regretted that the detailed maps, sections, and field notes referred to by 

 Mr. Glenn, which were deposited in the Survey Office, at Austin, have presumably been 

 destroyed. 



