The Atmosphere as a source of Nitrogen to Plants. 261 
it was found that the first rain falling, after a period of 3 weeks 
without rain, was very much richer in ammonia than usual. 
In the same year, M. Boussingault examined the water of dew 
and fogs, collected at Liebfrauenberg, and found them to be very 
rich in ammonia as compared with rain-water: a circumstance 
also sufficiently easy of explanation, since the deposition in the 
state of dew or fog of the watery vapour in the air, would 
necessarily be accompanied by that of the greater part of the 
ammonia present, and the quantity of water being comparatively 
small, would be proportionally rich in ammonia. The result of 
75 determinations of ammonia in rain-water, extending from the 
26th of May to the 8th of November, and including dew and 
fog, is stated by M. Boussingault to be, that the water contained 
on an average '0344 grains of ammonia in the imperial gallon. 
M. Boussingault, in the beginning of the year 1854, made 
determinations of ammonia present in the fogs of Paris, which 
he found to exceed very largely that existing in the fogs of the 
country. He also ascertained, a second time, the quantity present 
in rain falling in Paris, the result being to confirm very decidedly 
M. Barral's previous researches on the same subjects. 
In the years 1853 and 1854, Mr. Lawes and Dr. Gilbert made 
a series of determinations of ammonia in rain-water. A portion 
of their results was reported at the last meeting of the British 
Association at Liverpool ; unfortunately the volume of the Trans- 
actions for that meeting is not at the present moment (June 1st, 
1855) in publication, and I am unable to give any very definite 
account of their experiments. From a personal inspection of 
the arrangements, however, whilst these experiments were in 
progress, I know that they were conducted with that care and 
attention to detail which characterise all the researches of 
Mr. Lawes and Dr. Gilbert, and render them so worthy of trust. 
The Avater was collected in a rain-gauge, of very large size, 
representing a thousandth part of an acre, and placed at an 
elevation of several feet from the ground, in the middle of a 
field. The rain, as it fell, passed into large glass bottles prepared 
for its reception.* 
From the reason already given, I am only able to state that 
Messrs. Lawes and Gilbert's results were, in a great measure, con- 
firmatory of those made by M. Boussingault at Liebfrauenberg. 
The proportion of nitric acid was also determined in a great 
many quantities of rain-water. 
But Messrs. Lawes and Gilbert entertained so much doubt 
* Mr. Lawes's farm is situated at a distance of at least twenty miles in a direct 
line from London. He informed me, lio^vever, that when the wind came to him 
from the direction of the metropolis, the rain-water collected in the gauge was 
always slightly coloured by sooty particles. 
