Rothamsted Experimental Station. 
113 
soil on the Rothamsted estate contains little or no carbonate of 
lime ; but during the eighteenth century and earlier very large 
quantities of chalk were applied artificially, until it formed 
5 per cent, or so of the surface soil. This carbonate of lime is 
being dissolved out by the rain percolating through the soil. 
The rate at which it was being removed from the unmanured 
plots was shown by diagram. The rate of loss of carbonate 
of lime was increased by the use of manures containing 
ammonium salts, and diminished by the use of nitrate of soda 
or farmyard manure. 
The normal growth of crops tended to restore a certain 
amount of carbonate of lime or other base to the soil, because 
the plant, in feeding upon the neutral salts dissolved in the soil 
water, took more of their acids than of their bases, leaving 
behind a basic residue combined with carbonic acid excreted 
from the root. A diagram illustrated an experiment upon the 
growth of wheat, showing how the acids and bases with which 
the plant was supplied were eventually divided between the 
plant and the soil. A table was exhibited showing that with 
ordinary agricultural crops the restoration of base in this 
way must be considerable, probably supplying sufficient base 
for the nitrification process which is always going on. This 
explains why many soils containing little or no carbonate 
of lime remain healthy under ordinary cultivation, provided 
that acid manures like sulphate of ammonia or superphosphate 
are not used on them. 
Two turfs showed the appearance of grass land which had 
become sour and acid, and was in want of lime. Specimens 
showed weeds of the arable land indicating the same thing — 
samples of lime and chalk and manures, adding lime to the 
soil ; and manures which were acid and removed carbonate of 
lime from the soil. 
Two other turfs and a diagram illustrated one result of the 
former chalking of the Rothamsted soil : they had been taken 
from portions of land which had been allowed to run wild for 
the past twenty-four years, and thus carried a natural self-sown 
vegetation. One was taken from land which had been chalked, 
and now contained about 3 per cent, of carbonate of lime in 
the surface soil. The other was taken from another piece of 
land which had escaped the chalking process, and only 
contained about 02 per cent, of carbonate of lime in the 
surface soil. During the period of lying “ prairie,” the soil of 
the one had accumulated about 2,200 lb. of nitrogen per acre ; 
the soil of the other only about 950 lb. per acre. 
II. Cambridge University Agricultural Department. — The 
exhibit of the Cambridge University Department of Agricul- 
ture comprised three sections. The first section illustrated 
VOL. 66. I 
