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On the Food of Plants. 325 
‘These maritime plants appear to decompose a part of the 
soil in which they grow; the alkali produced by burning 
them, or the sal soda used in glass and soap, is évidently 
é genres by them from the muriatic salt. 
' Bat when we sce the Lichen parellus fixing itself on the 
siliceous rock, or the Lichen immersus affecting as it does 
the calcareous rock in preference to the siliceous ; whatever” 
may influence this choice, we cannot suspect that cither of 
these rocks contributes by its decomposition to the nutrition 
of these plants; nor, as I apprehend, have we reason to ima- 
gine that either chalk, sand, or clay, are im any form the 
-aliment of the plants. . 
Woollen rags have been found of great utility as a ma- 
nure, more especially for wheat. And in the experiments 
before us we may observe, that sand with rags produced a 
cabbage of two ounces, and four strong ears of wheat. In 
clay with rags our cabbage weiched role ounces, and we had 
twelve strong ears of wheat’ But in what manner these 
rags produced effect it is difficult’ to say, for in January 1797 
they were ‘not visilly decayed; and in the month of Sep- 
tember in that yer they still retained their texture. The 
quantity we usually spread upon one acre is not more than 
four or five cwt.; and yet in the experience of every farmer 
it is found that in the first year they néarly double the crop 
of wheat, and in the two succeeding years they yielded a 
visible increase. At present, therefore, we can’ merely re- 
cord it a3 a fact, that woollen rags are highly beneficial to 
the land: but we cannot pretend to say by what process they 
contribute to the nutriment of plants. 
Lime in our experiments was clearly detrimental with 
sand; the cabbage lived, but weighed less in January than 
when planted in July: the wheat had two slender’ stems’ 
In clay with lime our cabbage lived till December, but‘ ntver 
grew. The wheat had one stem, which was: ‘extremely sfen- 
der, and the ear was diminutive. na 
These facts appear discordant with the experience of far- 
mers in every quarter of the globe; for lime is found to be 
an excellent manure. In some parts of Wales’ they “have 
X 3 scarcely 
