REVIEWS. 337 



inclusive, are devoted to the detailed description of the local geology 

 of each of the counties embraced in this region. 



Part 11 (chapters XXI-XL inclusive) deals with the Economic Re- 

 sources of the Paleozoic group, which are limonite, hematite, manga- 

 nese ores, beauxite, coal, limestones, sandstones, and clays. The mode 

 of occurrence of these materials, their distribution both geographical 

 and geological, their analyses, etc., are shown forth in sufficient detail, 

 and a commendable feature of Dr. Spencer's treatment is found in the 

 explanations and suggestions as to the origin of these various ores, 

 expressed in terms which are easy of comprehension even by those 

 who have not had any special geological or chemical training. In this 

 way the book has a direct educational value apart from the great amount 

 of information as to local occurrences which it contains. The chapter 

 on beauxite is of special interest, because of recent developments in 

 the mining and shipping of this valuable substance from the Georgia 

 and Alabama mines. The occurrence and general character of the ore 

 in the two states are identical, in fact the ores belong practically to a 

 continuous deposit, in close connection with the strata of the Knox 

 Dolomite. On account of competition with the foreign beauxites, only 

 the higher grades of the ore. containing from 55 per cent, and upwards 

 of alumina, are shipped, and by far the greater part of this goes to the 

 making of alum. This seems a wanton waste, since the inferior grades 

 would answer for alum, and the higher grades should be reserved for 

 the manufacture of the metal. 



The coal of Georgia is confined to an area of about 200 square 

 miles on the plateaus of Sand and Lookout Mountains. It is furnished 

 almost entirely by two or three seams lying between the Upper and 

 Lower Conglomerates near the base of the Coal Measures, as is the 

 case also in Tennessee and the Plateau region of Alabama. In all this 

 territory, these seams and the strata by which they are separated, are 

 exceedingly variable in thickness. The most widely distributed of 

 these is the Castle Rock seam just below the Upper Conglomerate 

 (Main Etna and Cliff seams of Alabama and Tennessee). In Georgia 

 the Dade seam, some 30 feet or more below the preceding, appears 

 to be more extensively worked, and, in the sections given, of greater 

 average thickness. This seam also has been worked in Alabama, where 

 it is known as the Eureka seam. Still below this in all the states men- 

 tioned is another seam of great importance locally, the Red Ash seam. 



In one localitv, Round Mountain, which rises above the Lookout 



