116 Observations on Liehig^s " Organic Chemistry^' 



calcareous soils, which contain little potash, evidently because 

 the potash is not renewed. Soils formed from basalt, grey- 

 wacke, and porphyry are therefore, he says, best for meadow 

 land, on account of the potash they contain, from the reduced 

 feldspar. These soils, however, contain a good deal of alumina, 

 and will not part with their water and organic substances so 

 readily as the sandy soils. Some irrigated meadows in Germany, 

 he says, yield four times as much produce as others not ir- 

 rigated, and the fertility he attributes to the potash carried on 

 the meadows from the rivers which irrigate. There may how- 

 ever be organic substances deposited as well as potash: humus 

 is light and flocculent, and, if the soils irrigated are sandy, they 

 may be helped by alumina deposited if the rivers pass through 

 clayey soils ; part may be owing to these helps, as v^eW as to the 

 potash. The meadows irrigated from the common sewers, in 

 the neighbourhood of Edinburgh, yield more than four times an 

 ordinary produce ; it is the excrement deposited that is supposed 

 the cause. The quantity of potash, he says, in soils is inex- 

 haustible, when compared w^ith the quantity removed. If the 

 crop of grass, however, is increased by the gypsum, there is 

 more potash taken off than by a small crop, and it would ex- 

 haust the alkalies more; but in Germany they restore the 

 fertility, he says, by sprinkling the field with wood ashes, or the 

 lixiviated ashes of soap-boilers : these last should contain some 

 oil in solution with the ashes. The sandy heath of Luneburg 

 yields a crop only once every thirty or forty years, by burning 

 the heath, which yields the potash, he says, collected by rain 

 water during that time. There should also be charcoal from 

 the wood of the heath, and from the wood ashes above, to 

 produce carbonic acid and ammonia ; it, is, perhaps, necessary 

 to notice other benefits as well as the one under review. The 

 most decisive proof, he says, of the want of potash, is that of a 

 man at Bingen, who manured highly with horn shavings, which 

 contain little or no potash, and starved his vines ultimately, 

 though drawing very heavy crops for a while ; others who used 

 cow manure, though the crops were not so heavy at first, had 

 continued fruitfulness. A field also which was cropped with 

 wormwood, for the sake of collecting its ashes, was barren for a 

 long time afterwards; and woods where the young branches and 

 leaves were taken off got stinted in their growth, until they were 

 prohibited from being taken away, which restored their luxu- 

 riance. These all show forcibly the need of alkalies. I should 

 also ascribe part of the effect, in the first instance, to the vines 

 being allowed to overbear themselves, which in this country is 

 considered to exhaust the strength of the plant ; there is a vital 

 power in animals and plants, which all the alkalies and nitrogen 

 in the world will not replace, if it is trenched on, though they 



