On the Phosphoric Strata of the Chalk Formation. 
Gl 
covered with the detritus of other formations, the soil in its agri- 
cultural character is usually of a thinnish poor nature, though 
under good cultivation it can be made to produce excellent crops, 
especially of turnips, barley, and wheat. Upon these soils the 
application of bone manure has proved essentially beneficial — in 
fact it has been the means of reclaiming whole districts from 
sterility. Subsequent analyses of these chalks show them to be 
deficient in phosphoric acid : hence the cause of the benefit pro- 
duced by the application of phosphate of lime in the form of 
bone manure. The following is a partial analysis of the upper 
soft white chalk : — 
Carbonate of lime . . . . 96'06 
Phosphate of lime . . . . '26 
in 100 parts — with a little insoluble silicious matter, &c., not 
estimated. 
An examination of a portion of the hard white chalk without 
flints, though there were many fragments of fossil shells mixed 
up with the mass, gave scarcely a trace of phosphoric acid. 
The third division, or the chalk marl, contains more argil- 
laceous matter in its composilicm. It is generally of a soft texture 
and of a dirty-grey colour, and it readily decomposes into a fine 
powder when exposed to the vicissitudes of the weather. In 
many districts this stratum of marl has been extensively quarried 
for the purposes of manure ; and in earlier times it appears to 
have been applied to a much greater extent than in the present 
day. Wherever it outcrops, the soil is distinguished for its 
fertility. The prolific crops of wheat, beans, and clover which 
are grown with the aid of a comparatively small quantity of 
manure evince its productive capabilities. The application of 
bones has usually failed in producing any apparent benefit. Here 
again the analysis of this soil demonstrates one cause of the failure, 
by indicating a sufficient amount of phosphoric acid previously 
existing as one of its component parts. It has very generally 
been experienced that manures richly charged with nitrogenous 
matter have proved signally useful on this class of soils. An 
analysis of a specimen of this marl, taken from a pit whence 
thousands of loads had formerly been dug, gave the following 
results : — 
Insoluble silicious matter .... 19*64 
Soluble silica . . . . . . 6' 45 
Pliosphoric acid (equal to 3*75 bone-earth) . 1 '82 
Carbonic acid 28-98 
Lime 37-71 
Magnesia ....... "68 
Oxide of iron and alumina . , . . 3-04 
98-32 
