ALABAMA 1 29 



The Lower Measures, including the Etna conglomerate, nowhere ex- 

 ceed 300 feet along the east side of Raccoon in De Kalb county, and the 

 interval between Bonair and Etna is only 90 feet. In Marshall, on the 

 west side of Raccoon, the interval between the conglomerates is 70 feet, 

 and the Lower Measures at most 140 feet ; but within 10 miles south- 

 westwardly Mr Gibson estimates the Lower Measures at 800 feet and the 

 interval between the conglomerates at 500 feet. As will be seen, these 

 estimates approximate the thicknesses in Waldens ridge of Tennessee. 



The Etna or first conglomerate of Blount mountain is 50 to 100 feet 

 thick, and varies from a mass of rounded pebbles to a coarse grained 

 sandstone. The second conglomerate, unhesitatingly identified by Mr 

 Gibson with McCalley's upper conglomerate, the Bonair, is easily dis- 

 tinguished from the Etna, as its pebbles are less firmly cemented, and 

 where pebbles are absent the rock is light gray. Its thickness increases 

 southwestwardly, being 100 feet on Lime creek in Etowah county, while 

 midway in Blount mountain it is estimated at between 400 and 500 feet — 

 estimated because no measurements can be obtained. A third conglom- 

 erate, at approximately 1,000 feet above the Bonair, is composed of" good 

 sized, but not well rounded pebbles, firmly cemented together with car- 

 bonate of iron." A fourth conglomerate occurs very near the top of the 

 formation, about 1,250 feet above the third. Its upper portion is " light 

 colored, loosely cemented, and weathers badly, and is hence seldom seen 

 on the surface," but its place is shown by the abundance of large rounded 

 pebbles. The lower part is harder and better preserved. The total 

 thickness is not more than 55 feet, and the underlying rocks for 100 feet 

 are " quartzites." 



The interval between the Etna and Bonair is 110 feet in Etowah 

 county at a little distance from Lime creek. Two miles southwest, as 

 calculated from the dip, it is somewhat less than 250 feet. At 5 miles 

 farther it was thought to exceed 500 feet ; thence southwestwardly it de- 

 creases, becoming 100 feet or even less in the southwestern part of the 

 area. It is unfortunate that no detailed measurements of the higher 

 portions of the section are given for the northeastern part of the area. 

 Mr Gibson's map shows that measures to a considerable distance above 

 the third conglomerate are present at not more than 5 miles southwest 

 from Lime creek. It has been seen that the interval between Bonair 

 and Etna increases southwest from 90 feet in Etowah to possibly 500 

 feet on headwaters of Blackburns fork; that the Bonair increases in the 

 same distance from 110 to 400 feet or more, while the Lower Measures 

 increase from 300 to 800 feet. As all portions from the Bonair down- 

 ward show this extreme increase, one is led to surmise that the upper 

 portion increases in like manner. The temptation to suggest that the 



