BULLETIN OF THE BUSSEY INSTITUTION. 207 
earth which had been exposed to the air were at least twice as bulky 
as those from the earth that had been bottled. Indeed, the precipitates 
from the bottled earth appeared to be no larger than those obtained 
a month earlier from the earth that had been dried a week. It was 
noticed, however, that the percolates from the earth that had been 
exposed to the air were more highly colored than those from the 
bottled earth. 
Other samples of fresh loam, and of loam that had just been dried, 
taken from various localities, gave results similar to the foregoing. 
Some of these specimens were taken from cultivated fields, others 
from beneath sods both in woodland and in mowing fields. Most of 
them were from the Bussey Farm or its vicinity ; but one was from an 
old pasture at Rochester, Mass. Not one of these specimens gave 
any reaction with ammonia, when that substance was added to the 
percolates from the earths that had been spread out and left for two or 
three days in the glass house until they were air-dried. Most of them, 
on the other hand, gave abundant precipitates with ammonia, when 
percolated and tested, after having been exposed to the air in the glass 
house for one month. But there were exceptions to this rule, as will 
appear from the following statement : — 
Four specimens of earth were tested methodically, in such wise that the 
percolates from 1,000 grm. portions of the earths — both those recently 
dried, and those that had been dried a month — were contrasted, in respect 
to the amount of carbonic acid in each, and to the amount of solid matter 
left on evaporating a measured volume of the percolate. Half a litre of 
percolate was collected in each instance. All the percolates were tested 
with ammonia-water, also, to see if any precipitate would form. 
Each of these loams were taken fresh from the fields, and left to dry in 
the air two or three days, as above stated, before the first percolation, aud 
to dry in the air for a month before the second percolation. No. I. was 
loam from the Plain-field; No. II., loam from beneath the sod of a mowing 
field; No. III., from woodland beneath a pine tree; No. IV., subsoil that 
had been thrown aside by workmen in excavating a gravel pit. This 
earth (No. IV.) was very fine, though not clayey. It seemed to be well- 
nigh free from organic matter. 
It was found that 500 cc. of the percolates contained the following 
amounts of carbonic acid and of dry extract: — 
