The Atmosphere as a source of Nitrogen to Plants. 
249 
The present value of Down and Dorset fleeces, 13^/. to 
per lb. ; of lambs, about 18rf. to 20rf. per lb. 
Merino and Romney Marsh. — The fleece representing: this 
cross-breed is a very beautiful one ; an excellent combine: fleece ; 
fine, soft, clean, rich wool. When warps were made of worsted 
would have realised a very high value. 
The present value of hogs about 15f/. per lb. ; of wethers, 14c?. 
to W\d. per lb. 
XIV. — The Atmosphere as a Source of Nitrogen to Plants ; being 
an Account of Recent Researches on this subject. By J. Thomas 
Way, Consulting-Chemist to the Society. 
No reasoning on any law of nature is philosophical, or can lead 
us to the truth, unless it embraces a consideration of all existing 
conditions. A plant lives as it were in two elements : it has its 
roots in the eartli, it throws out branches and leaves to the air. 
How imperfect a notion should we form of the philosophy of 
vegetation, if we omitted from our consideration either the one 
or the other of these necessary conditions of vegetable life! 
Leaving apart, however, for the present, the first of these, we 
find, that from the earliest period of the development of true 
chemical philosophy, the composition of the atmosphere, in its 
relation to the processes of vegetable nutrition, has been a subject 
of repeated study ; to write a history of the successive steps by 
which, thanks to the labours of Lavoisier, Priestley, Bergman, 
Scheele, Black, Cavendish, and many others, we have arrived at 
our present knowledge of the composition of the air, would be to 
occupy unnecessarily the pages of this Journal. It is no part of 
my intention to enter further into the general question, than is 
necessary to direct the attention of the reader to the bearing of 
the particular branch of it which I have undertaken to discuss 
— that is to say, the atmospheric supply of nitrogen to plants. 
It will, however, be necessary to consider very shortly the 
composition of plants themselves, in order to see what the con- 
stituents are which they must by one means or another obtain. 
That the air does in some way materially affect the growth of 
plants, must have occurred to every mind that has been directed 
to these subjects. 
In the clefts of a rock, or on the ruin of a tower, the seed of a 
plant is driven by the wind, or dropped by a bird. By and bye 
moisture and warmth, the principal conditions of germination, 
cause the seed to grow into a plant, which has a more or 
less perfect existence, produces seed, withers and dies. In the 
succeeding years a further growth of the same kind occurs under 
