GEOLOGY. 



GEOLOGY. 



Porcelain earth was analyzed by Mr. Rose j 

 (Jameson's Min. vol. i. p. 298) : he found in it I 



Silica - 

 Alumina - 

 v Oxide of iron - 

 Loss - - - 



Parti. 



- 52' 



- 47- 



- 033 



- 0-67 



100- 



Potter's clay, according to M. Vauquelin, 

 contains 



Part*. 



Silica 43-5 



Alumina ....... 33 2 



Lime -...---- 35 



Oxide of iron --.--- 1* 

 Water- ------- 18- 



Loss 0-8 



100- 

 Clay tlate is composed of 



Parti. 

 Silica - ... ... 48-6 



Alumina - - 23'5 



Magnesia ... ... 16 



Peroxide of iron - - -113 



Oxide of manganese - ... 0'5 



Potash ... ... 4-7 



Carbon 0'3 



Sulphur .--.-.- 01 

 Water and volatile matter - - - 7 6 

 Loss 1-8 



100- 



Basalt is composed, according to Mr. Ken- 

 nedy (Edin. Trans, vol. v. p. 89), of 



Part.. 



Silica 48 



Alumina ...... -16 



Lime --9 



Soda --4 



Oxide of iron ... - 16 



Muriatic acid - - 1 



Water - - 5 



Loss - - 1 



Chlorite earth is composed of 



Silica - 

 Alumina 

 Lime - - 

 Oxide of iron 

 Potash 



100 



Parts. 



- 50- 

 . 26- 



- 15 



- 5' 



- 17 5 



100- 



Gypsum, of which there are several varieties, 

 is composed of 



Sulphate of lime 

 Water - - 



79-32 

 20-68 



100- 



The cultivator, therefore, must take it as an 

 axiom in his geological observations, that the 

 earthy composition of the surface soil almost 

 always partakes of the nature of the rock or 

 subsoil on which it immediately rests, and from 

 which, in fact, it has been generally thus 

 formed, in the progress of time, by various 

 external agencies. 



Alluvial soils, perhaps, are the most exten- 

 sive exceptions to this remark, for they are 

 formed commonly of the materials of different 

 strata, brought from various distances by the 

 flood waters, and mingled together, often in 

 very confused, yet most commonly in very 

 fertile p-oportions. (See ALLUVIUM.) Of this 

 description of soil there are in England many 

 534 



valuable tracts, such as that extending from 

 Lynn, through Lincolnshire to the Humber, 

 and thence to Bridlington. Both sides of the 

 valley of the Thames, about Sandwich in Kent, 

 Romsey Marsh, between Bristol and Bridge- 

 water, and Liverpool and Lancaster, and on 

 the banks of the rivers Forth and Tay in Scot- 

 land. " This kind of soil," says Mr. Morton, 

 "is always fertile, free in its nature, and easily 

 cultivated ; is fitted for the production of every 

 variety of crop, which it brings to the highest 

 perfection, and produces in the greatest abund- 

 ance. This formation is perfectly dry. About 

 one-half of all the alluvial accumulations may 

 be in tillage, and the remaining half in mea- 

 dow and pasture land." (On Soils, p. 10.) 



Diluvium is the geological name for those 

 masses of soil, composed of sand, gravel, &c., 

 which are found in many places, covering 

 some of the older formations. It is of various 

 composition : when it is found resting on the 

 tertiary and chalk formations, it is usually 

 composed of red clay and rounded flints. In 

 Dorsetshire the diluvium is commonly com- 

 posed of a mixture of sand and gravelly flints. 

 "Most of this soil," says Mr. Morton, "is in 

 arable culture, and produces turnips, barley, 

 oats, wheat, clover; and, when under proper 

 management, it becomes a useful soil. The 

 tenacious clay gravel is expensive in the culti- 

 vation, as it is most difficult to work, except 

 between wet and dry. The greatest improve- 

 ment which has been made in this soil is by 

 the application of chalk." The larger portion 

 of Suffolk and Norfolk is composed of a dilu- 

 vium sand, resting on chalk or marl. This 

 district is very level : it extends from Sudbury 

 to Bungay and Cromer, from Southwold to 

 Shelford, and from Swaffham to Yarmouth. 

 Resting as it does on a calcareous substratum, 

 the excellent cultivators of this district have 

 gradually and permanently improved the soil 

 by bringing the chalk or marl to the surface, 

 and spreading it aver the land at the rate of 

 about 100 cubic yards per acre ; in this way 

 mere rabbit warrens of blowing sands have 

 been improved so as to yield excellent crops 

 of corn, and rentals have been in this way 

 raised from a few pence to 20s. per acre. 



Peat Soils. These abound in many portions 

 of the United Kingdom. Their best mode of 

 improvement is, usually, by mixing them with 

 the earths. See PEAT SOILS. 



The Chalk Formation. This formation, very 

 common in England, but which does not exist 

 in the limits of the United Stales, is divided 

 by geologists into two divisions, the upper and 

 the lower chalk : the upper abounds in flints, 

 which are absent from the lower formation. 

 Chalk is chiefly carbonate of lime, with some 

 small portions of alumina, iron, and silica. "The 

 water which comes from below the lower 

 chalk," says Mr. Morton, " is pure and limpid, 

 and delicious to drink. It contains carbonate 

 of lime, and is of the best quality for watering 

 meadows ; hence the best water meadows are 

 in the chalk valleys." The soil of the chalk 

 formation is composed of chalk and flint in 

 various proportions. These soils are materi- 

 ally improved by a mixture with those of the 

 green sandstone formation, and by enclosing 



