298 THE EBGOLITH 



Chemical Analysis of Kaolin, Hockessin, Delaware 



Silica (SiOO 48.73% 



Titanic oxide (TiOa) 0.17 



Alumina (ALO3) 37.02 



Ferric iron (FeA) 0.79 



Lime (GaO) 0.16 



Magnesia (MgO) 0.11 



Potash (K^O) 0.41 



Soda (NaaO) 0.04 



Water at 100^ 0.52 



Ignition 12.83 



Phosphoric acid (PA) 0.03 



Total 100.81% 



Among the special names that have from time to time been 

 given to local phases of residuary accumulations, there remain 

 two, the laterite and Wacke, which are sufficiently common to 

 merit some attention. The first mentioned of these, laterite, 

 like loess and several other terms that might be mentioned, 

 has to a considerable extent lost its true lithological signifi- 

 cance through a careless usage. Originally the name was applied 

 to a vesicular highly ferruginous clay, soft in the mass, but hard- 

 ening on exposure to the weather, which has a wide distribu- 

 tion throughout India and Ceylon. Two forms are commonly 

 recognized, — the one capping the summits of hills and plateaux 

 on the highlands of central and western India, and underlaid 

 by the Deccan traps ; and the second occurring on the lowlands, 

 in part overlying gneisses and granites. The prevailing colors 

 of the laterite, when freshly broken, are various tints of brown, 

 red and yellow mottled, or whitish ; after exposure it is usually 

 covered with a brown or blackish-brown coating of limonite. 

 When first dug out, the material is sufficiently soft to be cut 

 with a pick or shovel, but becomes greatly indurated on expo- 

 sure. In some instances the material is of so compact a texture 

 and so hard as to resemble jasper. In many forms of laterite 

 the material is traversed by ''small irregular tortuous tubes 

 from a quarter of an inch to upwards of an inch in diameter." 

 These penetrate the mass in all directions, though most com- 

 monly nearly vertical, and are often lined with a coating of 

 limonite. On weathering, these give rise to extremely irregu- 

 larly pitted or scoriaceous surfaces, which, together with the 

 dense, often botryoidal structure, cause it to resemble certain 

 types of igneous rocks, for which it has more than once been 



