50 AMERICAN AGRICULTURE. 



ash and other substances. They are of much value as a 

 top-dressing for meadows. In addition to their furnishing 

 in themselves, a minute quantity of the food of plants, like 

 old plaster, they serve a much more extended purpose, by 

 condensing ammonia, nitric and carbonic acid, which they 

 give up to the demands of vegetation. They seem to fulfil the 

 same part as conductors, between the nutritive gases that 

 abound in the atmosphere and the vegetables which they 

 nourish, as the lightning rods in leading the electricity 

 from the clouds to the earth. 



CHARCOAL. 



When charcoal is scattered over the ground, it produces 

 the same effect as the foregoing, and probably in a greater 

 degree ; as it absorbs and condenses the various gases 

 within its pores, to the amount of from 20 to over 80 times 

 its own bulk. The economy and benefit of such applica- 

 tions, can be readily understood, as they are continually 

 gleaning these floating materials from the air, and storing 

 them up as food for plants. Charcoal as well as lime, often 

 checks rust in wheat, and mildew in other crops ; and in all 

 cases, mitigates their ravages, where it does not wholly 

 prevent them. 



BROKEN GLASS 



Is a silicate of potash or soda, according as either of these 

 alkalies are used in its manufacture. Silicate of potash, 

 (silex and potash chemically united,) is that material in 

 plants, which constitutes the flinty, exterior coating of the 

 grasses, straw, cornstalks, &c. ; and it is found in varying 

 quantity in all plants. 'It is most abundant in the bamboos, 

 cane, Indian corn, the stings of nettles, and the prickly 

 spikes in burs and thistles. Some species of the marsh- 

 grasses have these silicates so finely, yet firmly adjusted, 

 like saw-teeth, on their outer edges, as to cut the flesh to the 

 bone when drawn across the finger. Every farmer's boy 

 has experienced a yet more formidable weapon, in the sli- 

 vers from a cornstalk. 



It is to the absence of this material in peats and such other 

 soils, as have an undue proportion of animal or vegetable 

 manures, that we may attribute the imperfect maturity of 

 the grains and cultivated grasses grown upon them, causing 

 them to crinkle and fall, from the want of adequate support 

 to the stem ; and it is to their excess in sandy and cal- 



