438 Separation of Nitrogen from the Atmosphere. 
that traces of nitric acid are found in the rain that falls during 
thunderstorms ; and the observed increase of fertility which 
follows such thunderstorm rain is due, it is supposed, to the 
nitrogen carried to the roots of plants by the minute admixture 
of nitric acid in the rain which falls on such occasions. 
Also let us bear in mind the wonderful efficacy of a bloio, or per- 
cussive action, in bringing about a true chemical combination 
between certain elements which otherwise might lie for ever in 
close juxta-position without ever entering into chemical union. 
The efficacy of percussive force in this respect is well known in 
the case of all fulminating compounds. Viewing the thunder- 
storm effect above referred to as a percussive compressional 
agency, it occurred to me that we might attain the grand object 
of chemically combining the nitrogen and oxygen of the atmo- 
sphere, for the service of agriculture, by subjecting atmospheric 
air to exceedingly violent percussive compression in the presence 
of some cheap mineral substance which had a strong affinity for 
the nascent nitric acid, which I imagine would be the imme- 
diate result of such violent percussive compression. Dry slacked 
lime would appear to be the most suitable substance for effecting 
this object : the result would be nitrate of lime. Should we 
thus be so fortunate as to knock into combination the constituent 
elements of the atmosphere, and so produce a fertilizing agent of 
the most potent efficacy from an inexhaustible source at home, 
instead of, as at present, going for it, in the form of guano, all 
the way to Peru, a great result might ensue. Although this 
scheme has long afforded me subject for many a bit of quiet 
cogitation, I have as yet done nothing to bring it to the test of 
actual trial ; but as I have on many former occasions derived 
high gratification by giving forth such embryo schemes, and 
seen them come to life by the so planting them into the minds of 
intelligent men, I venture to promulgate my long-formed notions 
on this subject, in the hope that peradventure they may take root 
in favourable soil, and spring up and bear fruit in due season. 
Even at the risk of being thought a propounder of a visionary 
scheme in the meanwhile, and even failing the realization of any 
commercially valuable result, the issue might prove acceptable 
in a purely scientific point of view. 
As some aid to others who might be inclined to practically 
test my ideas on this subject, I append hereto a rough sketch of 
an apparatus by which this interesting investigation might be 
put to the test of actual experiment. Once establish the fact 
that by percussive compression nitric acid can be produced 
by direct combination of the elements of our atmosphere, the 
solution of the commercial part of the problem would be in a fair 
