m THE ASSIMILATION OF NITROGEN FROM THE AIR BY PLANTS, 
143 
arrived at a certain amount of obesity, it would 
merely become a consumer of food without any 
commensurate advantage. On the other hand, 
the larger animal would be constantly develop¬ 
ing its frame; and when fully matured, I have 
my doubts whether any animal yields so large 
a return of meat for the quantity of food con¬ 
sumed as selected mature animals of the Old 
English breed. In this respect, the improved 
Berkshire bears an intermediate place between 
the smaller and the larger breed, arriving at 
maturity earlier; but I doubt, when fully grown, 
whether it puts on the same quantity of flesh 
for an equal amount of food, and in so short a 
space of time as the old large breed at maturity. 
Of the three breeds now named by way of illus¬ 
tration, my own experience leads me to decide 
that for all purposes, whether as fresh pork, 
pickled pork, ham, and bacon, the merrifcs of 
the improved Essex exceeds all other kinds; 
that the improved Berkshire follows; whilst 
the old large kind is a mere bacon pig; as such, 
however, it is highly esteemed in the farm 
house; the huge flitch, with its great depth of 
fat, being considered the most economic food 
for the laborer—in which opinion he will be 
found to concur, as whenever he has a choice, 
or from circumstances is compelled to purchase 
for himself he will always be found to prefer 
the thick fat part of the flitch .—Journal of the 
Royal Ag. Soc . 
- -©»- 
ON THE ASSIMILATION OF NITROGEN FROM THE 
AIR BY PLANTS, AND ON THE INFLUENCE 
OF AMMONIA IN VEGETATION. 
Many years ago, M. de Saussure remark¬ 
ed that a solution of sulphate of alumina be¬ 
came, if exposed to the air for a sufficient 
length of time, converted into ammoniacal alum. 
This observation, made in the year 1804, dem¬ 
onstrated the existence of ammonia in the at¬ 
mosphere. Since the time of M. de Saus¬ 
sure, many chemists have endeavored to ascer¬ 
tain the quantity of ammonia that exists in the 
air by more expeditious and more exact meth¬ 
ods. The importance attributed by physiolo¬ 
gists to ammoniacal compounds in the develop¬ 
ment of plants, was the cause of these endeav¬ 
ors made by the chemists. It is the general 
opinion that the source from which plants de¬ 
rive their nitrogen is ammonia existing either 
in the soil itself, or in the manure laid upon it, 
or in the atmosphere. 
After having satisfied myself, by a long se¬ 
ries of experiments made on much larger quan¬ 
tities of air than have been analysed by my 
predecessors, that the quantity of ammonia in 
the atmosphere is scarcely appreciable, if pains 
be taken to avoid sources of error which may 
be caused by accidental emanations of the gas, 
I was led to doubt the reality of the influence 
attributed to ammonia in vegetation. 
To clear up these doubts, T sowed a certain 
number of seeds in a mixture of equal quanti¬ 
ties of white sand and brick dust, which had 
been previously calcined, for many days, in a 
porcelain furnace, in order that all organic 
matter in them might be utterly destroyed. 
This mixture was placed in a certain number 
of pots, and to it was added 5 per cent, of ashes 
obtained by the combustion of the plants with 
the seeds of which I was experimenting. The 
pots were placed under a bell glass, hermeti¬ 
cally sealed. The air inside the glass was re¬ 
newed every day by means of a very large as¬ 
pirator (containing 631 litres at zero, under a 
pressure of 760). But as this quantity of ail', 
though large, did not contain sufficient carbonic 
acid for the purposes of vegetation, 5 and after¬ 
wards 7 per cent, of this gas was added by 
means of an apparatus from which the gas es¬ 
caped bubble by bubble, during the whole of 
the time occupied by the renewing of the air. 
The air which came out from the bell glass was 
conducted into an apparatus in which all the 
ammonia present in the air was separated from 
it. 
Thus two experiments went on at the same 
time; in the first, I dosed the ammonia with a 
certain quantity of pure air; and in the second 
the ammonia with a nearly equal quantity of 
air, which had nourished the plants under 
the bell glass. By comparing the results of 
these two analyses, I was enabled to see wheth¬ 
er the ammonia of the air had taken any part 
in the development of the plants. On the other 
hand, by previously analysing a certain num¬ 
ber of seeds similar to those with which I was 
experimenting, I ascertained how much nitrogen 
was introduced under the bell glass in the seeds. 
When the experiment is finished, I shall be 
able to ascertain, by similar analyses, the quan¬ 
tity of nitrogen assimilated during the experi¬ 
ment ; and from that again, whether this nitro¬ 
gen was derived from the ammonia or the ni¬ 
trogen of the air. 
Although the plants have not yet been taken 
out of the apparatus, the question may be con¬ 
sidered as determined. It is quite clear that a 
certain quantity of nitrogen has been assimi¬ 
lated by the plants, and this nitrogen was de¬ 
rived from that of the air; for the plants under 
the glass have become developed in a remark- 
