From a morgen of good meadow land, 2,500 pounds weight of hay, according to the best agriculturists, are obtained on an average.  This amount is furnished without any supply of organic substances, without manure containing carbon or nitrogen.  By irrigation, and the application of ashes or gypsum, double that amount may be grown.  But assuming 2,500 pounds weight of hay to be the maximum, we may calculate the amount of carbon and nitrogen derived from the atmosphere by the plants of meadows.

According to elementary analysis, hay, dried at a temperature of 100 deg Reaumur, contains 45.8 per cent. of carbon, and 1 1/2 per cent. of nitrogen. 14 per cent. of water retained by the hay, dried at common temperatures, is driven off at 100 deg. 2,500 pounds weight of hay, therefore, corresponds to 2,150 pounds, dried at 100 deg.  This shows us, that 984 pounds of carbon, and 32.2 pounds weight of nitrogen, have been obtained in the produce of one morgen of meadow land.  Supposing that this nitrogen has been absorbed by the plants in the form of ammonia, the atmosphere contains 39.1 pounds weight of ammonia to every 3640 pounds weight of carbonic acid (=984 carbon, or 27 per cent.), or in other words, to every 1,000 pounds weight of carbonic acid, 10.7 pounds of ammonia, that is to about 1/100,000, the weight of the air, or 1/60,000 of its volume.

For every 100 parts of carbonic acid absorbed by the surface of the leaves, the plant receives from the atmosphere somewhat more than one part of ammonia.

With every 1,000 pounds of carbon, we obtain—­

From a meadow . 32 7/10 pounds of nitrogen.

From cultivated fields,

In Wheat . 21 1/2 " "

Oats . 22.3 " "

Rye . 15.2 " "

Potatoes . 34.1 " "

Beetroot . 39.1 " "

Clover . 44 " "

Peas . 62 " "

Boussingault obtained from his farm at Bechelbronn, in Alsace, in five years, in the shape of potatoes, wheat, clover, turnips, and oats, 8,383 of carbon, and 250.7 nitrogen.  In the following five years, as beetroot, wheat, clover, turnips, oats, and rye, 8,192 of carbon, and 284.2 of nitrogen.  In a further course of six years, potatoes, wheat, clover, turnips, peas, and rye, 10,949 of carbon, 356.6 of nitrogen.  In 16 years, 27,424 carbon, 858 1/2 nitrogen, which gives for every 1,000 carbon, 31.3 nitrogen.

From these interesting and unquestionable facts, we may deduce some conclusions of the highest importance in their application to agriculture.

1.  We observe that the relative proportions of carbon and nitrogen, stand in a fixed relation to the surface of the leaves.  Those plants, in which all the nitrogen may be said to be concentrated in the seeds, as the cerealia, contain on the whole less nitrogen than the leguminous plants, peas, and clover.

2.  The produce of nitrogen on a meadow which receives no nitrogenised manure, is greater than that of a field of wheat which has been manured.