GEOGNOSY AND GEOLOGY. 11] 
Clay Shale, an earthy clay of more or less slaty structure, and of a grey 
color, running into black by the addition of carbonaceous matter. It has 
a powerful attraction for water ; so much so, that when the tongue is touched 
by a small piece the two adhere firmly. 
Clay. Of an earthy consistence, and readily rendered plastic by water. 
It contains sand more or less easily removable by washing. Several kinds 
are distinguished : 
Porcelain Clay. Of a white color, which is permanent in baking. It 
is closely allied to kaolin, or clay resulting from the decomposition of 
feldspar. 
Pipe Clay. Of a grey color, produced by a slight admixture of bituminous 
matter. This clay becomes white by burning, and is well adapted to the 
manutacture of tobacco pipes and common ware. 
Potters’ Clay. Of various colors, grey, yellow, and reddish-brown. 
Loam. ‘This occupies a place intermediate between clay and sand; it is 
of an earthy and sandy feel. The sand, distributed in great quantity, 
although not always visible, may readily be felt. Colors grey, brownish, and 
reddish. When it contains much lime it becomes marl loam. 
Series 2. Soils. 
This series embraces thorough and loose mixtures of various substances. 
The conditions of aggregation, as well as the colors, are exceedingly 
diversified, these being modified principally by a greater or less proportion 
of humose substance, and by iron, and perhaps manganese combinations. 
The different soils vary much in their capacity of taking up water. The 
weathering of various rocks, as well as their mechanical separation or 
division, is the principal source from which they are derived; for this 
reason their composition is of great diversity. Lime, magnesia, potassa, 
soda, and oxydes of iron and manganese, are of most general occurrence as 
bases, these being combined with carbonic, silicic, sulphuric, phosphoric, and 
nitric acids, as also with chloric and fluoric. The organic matters consist 
of vegetable mould under various forms, as humus, geine, ulmine, humic 
and ulmic acids. Salts of ammonia also occur. Particular kinds are 
determined by the predominance of individual ingredients; the full investi- 
gation of these soils and their properties belongs not to this subject but to 
agriculture. The principal of these soils are : 
Clayey Earth. An earthy mass with clay in excess. It absorbs a large 
quantity of water, thereby becoming plastic; on drying again it becomes 
very hard, and exhibits extensive cracks and fissures, owing to the shrinking 
in volume. The consistence of the soil is generally solid. Grey, yellow, 
brownish, and bluish, are the most conspicuous colors. 
Loamy Soil. This occupies a position intermediate between a clayey 
and a sandy soil, just as loam does between clay and sand. The earthy 
mass is generally of a brownish or yellowish-grey color, furnishing a 
fruitful land when calcareous particles enter also into combination. 
Sandy Soil. This contains an excess of quartzose sand, in an earthy, 
clayey, or marly mass. It is very loose, and of a grey, yellowish, or whitish 
color, takes up little water, parts with it readily, and quickly becomes dry. 
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