616 



FARMERS' REGISTER 



[No. If 



3. Alumina exists in a pure and crystallized 

 state in the white sapphire, and united to a little 

 oxide of iron and silica in the other oriental gems. 



In the state in which it is procured by chemists, 

 it appears as a white powder, soluble in acids and 

 fixed alkaline liquors. From my experiments, it 

 appears that alumina consists of one proportion 33 

 of aluminum, and one 15 of oxygen. 



4. Magnesia exists in a pure crystallized state, 

 constituting a mineral like talc found in North 

 America. In its common form it is the magnesia 

 usia, or calcined magnesia of druggists. It ge- 

 nerally exists in soils combined with carbonic acid. 

 It is soluble in all the mineral acids ; but not in 

 alkaline lixivia. It is distinguished from the other 

 earths found in soils by its ready solubility in so- 

 lutions of alkahne carboneites, saturated with car- 

 bonic acid. It appears to consist of 38 magnesium 

 and 15 oxygen. 



5. There are two well-known oxides of iron, 

 the black and the brown. The black is the sub- 

 stance that flies off when red-hot iron is ham- 

 mered. The brown oxide may be fbimed by 

 keeping the black oxide red-hot lor a long time in 

 contact with air. The first seems to consist of 

 one proportion of iron 103, and two of oxygen 30 : 

 and the second of one proportion of iron 103, and 

 three proportions of oxygen 45. The oxides of 

 iron sometimes exist in soils combined with car- 

 bonic acid. They are easily distinguished from 

 other substances by their giving, when dissolved in 

 acids, a black color to solution of galls, and a 

 bright blue precipitate to solution of prussiate of 

 potassa and iron. 



6. The oxide of manganesum is the substance 

 commonly called manganese, and used m bleach- 

 ing. It appears to be composed of one proportion 

 of manganesum 113, and three of oxygen 45. It 

 is distmguished from the other substances found 

 in soils, by its properly of decomposing muriatic 

 acid, and converting it into chlorine. 



7. Vegetable and animal matters are known by 

 their sensible qualities, and by their property of be- 

 ing decomposed by heat. Their characters may 

 be learned I'rom the details in the last lecture. 



8. The saline compounds found in soils, are 

 common salt, sulphate of magnesia, sometimes 

 sulphate o? iron, nitrates of lime and of magne- 

 sia, sulphate of potassa, and carbonates of pot- 

 assa and soda.* To describe their characters mi- 

 nutely will be unnecessary : the tests for most of 

 them have been already noticed. 



The silica in soils is usually combined with 

 alumina and oxide of iron, or with alumina, lime, 

 magnesia, and oxide of iron, forming gravel and 

 sand of different degrees of fineness. The car- 

 bonate of lime is usually in an impalpable Ibrm ; 

 but sometimes in the state of calcareous sand. 

 The magnesia, if not combined in the gravel and 

 sand of soil, is in a fine powder united to carbonic 

 acid. The impalpable part of the soil, which is 

 usually called clay or loam, consists of silica, 

 alumina, lirne, and magnesia ; and is, in fact, 

 usually of the same composition as the hard sand, 

 but more finely divided. The vegetable or ani- 



* In some soils, especially in Spain and in Bengal, 

 nitre is an ini^redient formed by the intervention of 

 carbonate of lime, by the union of alkali in the soil, 

 and of nitric acid, the elements of which are derived 

 from the atmosphere. — J. D. 



mal matters (and the first is by far the most com- 

 mon in soils), exist in different states of decom- 

 position. They are sometimes fibrous, sometimes 

 entirely broken down and mixed with the soil. 



To form a just idea of soils, it is necessary to 

 conceive different rocks decomposed, or ground 

 into parts and powder of different degrees of fine- 

 ness, some of their soluble parts dissolved by wa- 

 ter, and that water adhering to the mass, and the 

 whole mixed with larger or smaller quantities of 

 the remains of vegetables and animals in differ- 

 ent stages of decay. 



It will be necessary to describe the processes by 

 which all the varieties of soils may be analyzed, 

 I shall be minute in these particulars, and, I fear, 

 tedious; but the philosophical farmer will, I trust, 

 feel the propriety of full details on this subject. 



The instruments required for the analysis of 

 soils are few, and but little expensive. They are, 

 a balance capable of containing a quarter of a 

 pound of common soil, and capable of turning 

 when loaded with a grain ; a set of weights from 

 a quarter of a pound troy to a grain ; a wire sieve, 

 sufficiently coarse to admit a mustard seed through 

 its apertures ; an Argand lamp and stand ; some 

 glass bottles ; Hessian crucibles ; procelain, or 

 queen's ware evaporating basins ; a Wedgewood 

 pestle and mortar ; some filters made of half a' 

 sheet of blotting paper, folded so as to contain a 

 pint of liquid, and greased at the edges ; a bone 

 knife, and an apparatus for collecting and mea- 

 suring aeriform fluids. 



The chemical substances or re-agents required 

 for separating the constituent parts of the soil, 

 have, for the most part, been mentioned before ; 

 they are muriatic acid (spirit of salt,) sulphuric 

 acid, pure volatile alkali dissolved in water, solu- 

 tion of prussiate of potash and iron, succinate of 

 ammonia, soap lie, or solution of potassa, solutions 

 of carbonate of ammonia, or muriate of ammonia, 

 of neutral carbonate of potash, and nitrate of am- 

 moniac. 



In cases when the general nature of the soil of 

 a field is to be ascertained, specimens of it shonld 

 be taken from different places, two or three inches 

 below the surface, and examined as to the simi- 

 larity of their properties. It sometimes happens, 

 that upon plains the whole of the upper stratum 

 of the land is of the same kind, and in this case 

 one analysis will be sufficient ; but in valleys, and 

 near the beds of rivers, there are very great dif- 

 ferences, and it now and then occurs that one part 

 of a field is calcareous, and another part siliceous ; 

 and in this case, and in analogous cases, the por- 

 tions different fi-om each other should be separate- 

 ly submitted to experiment. 



Soils, when collected, if they cannot be imme- 

 diately examined, should be preserved in phials 

 quite filled with them, and closed with ground- 

 glass stoppers. 



The quantify of soil most convenient for a per- 

 fect analysis, is from two to four hundred grains. 

 It should be collected in dry weather, and exposed 

 to the atmosphere till it becomes dry to the touch. 



The specific gravity of a soil, or the relation of 

 its weight to that of water, may be ascertained by 

 introducing into a phial, which will contain a 

 known quantity of water, equal volumes of water 

 and of soil ; and this may be easily done by pour- 

 ing in water till it is half full, and then adding the 

 soil till the fluid rises to the mouth ; the difference 



