338 THE JOURNAL OF GEOLOGY. 



Table land as a prominent eminence, an important seam is described 

 by Dr. Spencer, which lies many feet higher up in the measures, and 

 which so far as we know does not occur in that part of Lookout Moun- 

 tain that extends into Alabama. 



The clays described are of several kinds, (i) the kaolin-like clays^ 

 (2) the residual clays from the decomposition of limestones and cal- 

 careous shales, (3) the clays formed from the disintegration of shales, 

 and (4) the alluvial clays. The first variety occurs in " horses " or in 

 sheets or pockets in the residual earths from the decomposition of the 

 strata of the Knox Dolomite and Fort Payne series. These are often 

 quite pure and white, and have nearly the theoretical composition of 

 kaolin. Although they occur in the residual matters they are not,, 

 according to Dr. Spencer, residua of the limestones, but are derived 

 from the rocks of the metamorphic series. 



The residual clays produce sometimes fairly good brick, but they 

 are generally too rich in fusible materials to make fine products. Of 

 greatest promise are the clays derived from the disintegration of shales 

 and slates, some of which have given beautiful vitrified brick, such as 

 would probably be well suited to serve as paving brick. The alluvial 

 clays, especially such as belong to the Second Bottom deposits, in 

 Georgia as well as in Alabama and Mississippi, furnish by far the 

 greater part of the material for the manufacture of ordinary building 

 brick, and it is of interest to note that the best quality of building 

 brick along the whole Appalachian region is made from deposits of 

 this character. 



In chapters XL and XLI we have a plea for better roads, with 

 numerous illustrations of country roads in Europe and America, which 

 emphasize sufficiently well the contrast between good roads and bad 

 ones. This is a seasonable chapter in view of the great interest now 

 being awakened in the subject of better roads throughout the southern 

 states. 



Part III, chapters XLII to XLIV, is devoted to the discussion of 

 the origin and characteristics of the soils derived from the various 

 Paleozoic formations, and the composition of these soils is shown also 

 by a number of chemical analyses. 



An appendix containing acknowledgments and an account of the 

 progress of the Survey, a classified table of contents and a full index 

 conclude the volume. The base of the map has been compiled chiefly 

 from the topographic sheets of the U. S. Geological Survey, and in the 



