118 OF THE INORGANIC CONSTITUENTS OF PLANTS. 



not the case in a meadow, and hence we never find a 

 luxuriant crop of grass * on sandy and calcareous 

 soils, which contain little potash, evidently because 

 one of the constituents indispensable to the growth 

 of the plants is wanting. Soils formed from basalt, 

 grauwacke, and porphyry, are, cceteris paribus, the 

 best for meadow-land, on account of the quantity of 

 potash which enters into their composition. The 

 potash abstracted by the plants is restored during 

 the annual irrigation. The potash contained in the 

 soil itself is inexhaustible in comparison with the 

 quantity removed by plants. But when we increase 

 the crop of grass in a meadow by means of gypsum, 

 we remove a greater quantity of potash with the hay 

 than can under the same circumstances be restored. 

 Hence it happens that, after the lapse of several 

 years, the crops of grass on the meadows manured 

 with gypsum diminish, owing to the deficieacy of 

 potash. But if the meadow be strewed from time to 

 time with wood-ashes, even with the lixiviated ashes 

 which have been used by soap-boilers, (in Germany 

 much soap is made from the ashes of wood,) then 

 the grass thrives as luxuriantly as before. The ash- 

 es are only a means of restoring the potash, f 



* It would be of importance to examine what alkalies are contained 

 in the ashes of the seashore plants which grow in the humid hollows 

 of downs, and especially in those of the millet-grass. If potash is not 

 found in them, it must certainly be replaced by soda as in the Salsola^ 

 or by lime as in the PlumbaginecB. — L. 



t The compost which has been employed with most advantage as a 

 top dressing to grass by Mr. Haggerston, on the estate of J. P. Gushing, 

 Esq., at Watertown, is prepared from peat and barilla alone. 



The peat previously cut and dried is made into heaps with alternate 

 layers of barilla, the thickness of each layer of peat being eight inches, 

 and of the barilla four inches. This heap is allowed to remain undis- 

 turbed during the winter, in the spring it is carefully turned and then 

 allowed to remain until the ensuing autumn, when it is spread upon 

 the land. 



Peat which is to be ploughed into the land, having been deposited in 

 the yard to which swine have free access, is mixed with stable manure 

 in the proportion of two thirds peat to one third manure. 



Barilla is the crude soda which is imported from Spain, Sicily, &c., 

 where it is prepared by burning the plant called salsola soda. Accord- 

 ing to Dr. Ure it contains 20 per cent, of real alkali (soda) with muri- 

 ates and sulphates of soda, some lime and alumina, with very little 

 sulphur. 



