air appears to have
been first observed by Priestley at the end of the last century, but
Liebig, in 1825, showed that it was always to be found after
thunder-storms, although he failed to detect it at other times. In 1851
Barral proved that it is invariably present in rain-water, and stated
the quantity annually carried down to an acre of land at no less than
41.29 lbs. But at the time his experiments were made, the methods of
determining very minute quantities of nitric acid were exceedingly
defective, and Way, by the adoption of an improved process, has shown
that the quantity is very much smaller than Barral supposed, and really
falls short of three pounds. His results for ammonia, as well as nitric
acid, are given in the subjoined table.

---------------------+----------------+----------------+-----------------+
| | Nitric Acid in | Ammonia in | Total Nitrogen |
| | Grains. | Grains. | in Grains. |
| +-------+--------+-------+--------+--------+--------+
| | 1855. | 1856. | 1855. | 1856. | 1855. | 1856. |
+--------------------+-------+--------+-------+--------+--------+--------+
|January | 230 | 1564 | 1244 | 5,005 | 1084 | 4,526 |
|February | 944 | 544 | 2337 | 4,175 | 2169 | 3,579 |
|March | 1102 | 866 | 4513 | 2,108 | 3995 | 1,945 |
|April | 325 | 1063 | 1141 | 8,614 | 1024 | 7,369 |
|May | 1840 | 3024 | 4206 | 18,313 | 3939 | 15,863 |
|June | 3303 | 2046 | 5574 | 4,870 | 5447 | 4,540 |
|July | 2680 | 1191 | 9620 | 2,869 | 8615 | 2,670 |
|August | 3577 | 2125 | 4769 | 4,214 | 4870 | 4,021 |
|September | 732 | 1756 | 3313 | 5,972 | 2917 | 5,373 |
|October | 4480 | 2075 | 7592 | 3,921 | 7414 | 3,767 |
|November | 1007 | 1371 | 3021 | 2,591 | 2749 | 2,489 |
|December | 664 | 2035 | 2438 | 4,070 | 2180 | 3,352 |
+--------------------+-------+--------+-------+--------+--------+--------+
|Total in pounds for}| | | | | | |
|the whole year }| 2.98 | .280 | 7.11 | 9.53 | 6.63 | 8.31 |
+--------------------+-------+--------+----------------+--------+--------+

No attempts have been made to determine the proportion of ni