EARTHS. 



mina. This earth, however, necessarily exists 

 in all fertile soils as the food of plants ; for 

 although the proportions in which it is found 

 are rather small, yet still there is no reason to 

 believe that its presence is not essential to the 

 healthy growth of the plant M. Saussure 

 found the ashes of the Pinus abies, growing on 

 a granitic and on a calcareous soil, to contain 

 nearly the same quantity of alumina (15 per 

 cent, on the calcareous and 16 per cent, on the 

 granitic), although these soils differed widely 

 in the proportion of the alumina they contained' ; 

 for 100 parts of each wood were composed of: 



The Granitic Soil. Parts. 



Silica ....... 7525 



Alumina 13-25 



Lime 1-74 



Iron and manganese .... ;i HII 



EARTHS. 



The Calcareous Soil. 

 Carbonate of lime 

 Alumina - 

 .Oxide of iron - 

 Petroleum . . . 



9924 



- 98-000 



- 0-625 



- 0-625 



- 0025 



99-275 



(Thomson's Chem. vol. iv. p. 317.) 



Such are the earths which constitute . all 

 cultivated soils, and such is the necessary pro- 

 portion in which they form the constituent 

 elements of some of the plants which they sup- 

 port. In the soils of the cultivator, however, 

 they exist in an endless variety of proportions : 

 thus, I found 68-5 per cent, of silica in the 

 gravelly soils of Great Totham, in Essex, and 

 62 in those of Kintbury, in Berkshire. Davy 

 discovered about 50 per cent, in the soil of the 

 Endsleigh Pastures in Devonshire, 54 in that 

 near Sheffield Place in Sussex, 15 in the turnip 

 soils of Holkham in Norfolk, 32 in the finely 

 divided matters of the wheat soils of West 

 Drayton, and about 97 per cent, in the soil of 

 Bagshot Heath. Mr. George Sinclair found 

 about 66 per cent in the grass garden of Wo- 

 burn Abbey. 



Of alumina, or pure earth of clay, the pro- 

 portions are equally varying. I ascertained 

 the presence of 4-5 per cent, of this earth in a 

 gravelly soil of Thurstable in Essex, and 8-5 in 

 one at Kintbury in Berkshire. Mr. G. Sinclair 

 found 14 per cent in the soil of the grass gar- 

 den at Woburn Abbey. Davy detected 8'5 per 

 cent, in that at Endsleigh, 6-25 in one at Croft 

 Church in Lincolnshire, 7 in that in Sheffield 

 Place, 11 in that of Holkham, 29 in a field at 

 West Drayton, and about 1 per cent, in the soil 

 of Bagshot Heath. 



Of carbonate of lime, the presence is just 

 as varying in amount as that of the other 

 earths. I found 18 per cent, in a soil at To- 

 tham, and 19 per cent, in a soil at Kintbury; 

 Sinclair, 2 per cent, in the soil of the Woburn 

 Abbey grass garden. Davy discovered 8 per 

 cent, in that from Croft Church, 3 per cent in 

 that of Sheffield Place, 63 per cent, in the finely 

 divided matters of the soil from Holkham, 

 and about 1 per cent only in the soil from 

 Bagshot 



The farmer, however, must not conclude, that 

 by merely mixing the pure earths, silica, lime, 

 and alumina together in the most fertile pro- 

 430 



portion, a soil can be formed on which plants 

 will flourish, for such is a very erroneous con- 

 clusion. All attempts which have been made 

 to make plants flourish in the pure earths have 

 failed utterly when they have been watered 

 with pure water ; yet a totally different result 

 I have invariably experienced when I have 

 employed an impure solution or liquid manure. 

 My trials have been entirely supported by 

 .those of M. Giobert, who having formed of the 

 four earths, silica, alumina, lime, and magne- 

 sia, a soil in the most fertile proportion, in vain 

 essayed to make the plants flourish in it when 

 watered with pure water only; but every diffi- 

 culty was removed when he moistened it with 

 the water from a dunghill, for they then grew 

 most luxuriantly; and M. Lampadius still fur- 

 ther demonstrated the necessity for, and the 

 powers of such an addition to the soil ; for he 

 formed plots composed only of a single earth 

 namely, pure lime, pure alumina, or pure 

 silica and plarited .in each different vegeta- 

 bles, watering them with the liquid drainings 

 from a dunghill, and he found that plants on 

 all of them flourished equally well. The solu- 

 ble matters of a soil ever constitute, in fact, its 

 most fertilizing portion ; and if by any artificial 

 means the richest mould is deprived of these, 

 as by repeated washings in cold or boiling 

 water, the residuum or remaining solid matter 

 is rendered nearly sterile. This fact, first ac- 

 curately demonstrated by M. Saussure, I have 

 since confirmed by a variety of experiments. 

 Neither must the cultivator imagine that these 

 carefully considered conclusions, the results 

 of often-repeated laborious experiments, are 

 erroneous, because transparent water, appa- 

 rently pure, when viewed in water-glasses, or 

 in irrigation, promotes the growth of bulbs, 

 grass, &c., since the very purest spring water, 

 even rain water, contains foreign substances; 

 and when only chemically pure water is em- 

 ployed to water plants, they cannot be made 

 to flourish. I have fruitlessly varied the at- 

 tempt in several ways. All the experiments of 

 Dr. Thomson were equally unsuccessful, the 

 plants vegetating only for a certain time, and 

 never perfecting their seeds. Similar experi- 

 ments were made by Hassenfratz, Saussure, 

 and others, with the same unfavourable result. 

 Duhamel found that an oak, which he had 

 raised from an acorn in common water, made 

 less and less progress every year. The florist 

 is well aware that bulbous roots, such as those 

 of hyacinths, tulips, <Scc., which are made to 

 grow in water, unless they are planted in the 

 earth every other year, at first refuse to flower, 

 and finally they cease even to vegetate. More- 

 over, it has been unanswerably shown by 

 many very accurate experiments, at the repe- 

 tition of which I have personally assisted, that 

 the quantity of nourishment or solid matters 

 absorbed by the roots of plants is always in j 

 proportion to the impurity of the water with i 

 which they are nourished ; thus some common 

 garden beans were made to vegetate under 

 three different circumstances; the first were 

 grown in distilled water, the second were 

 placed in sand and watered with rain water, the 

 third were sown in garden mould. The plants 

 thus produced, when accurately analyzed, 



