THK BROADBALK WHEAT SOILS. 
59 
according to the crop grown and according to other circumstances, 
bm that in the subsoils of the second to the sixth or seventh depths 
it gmdoaDy declines, although the mean percentage is very similar at 
corresponding depths in t lie three fields — Broadbalk, Boos, and 
Agdell. Below the sixth < 1 « * i>r li . however, there is less evidence of 
any regular declension either in I loos or Agdell field, but in the case 
of the Broadbalk soils the percentages rang'' distinctly lower than in 
the other fields. Reference to notes made at the time of collection of 
the samples, however, showslhat these lower percentages are to be 
correlated with larger proport ions of sand or chalk intermixed with 
the clay subsoils, the mingling of chalk especially all'ecting the lowest 
depths. It is to be observed thai in the case of the other fields the 
normal clayey subsoil of the six lower depths contains an average of 
rather over 'U>4 per cent of nitrogen, as determined by soda-lime, 
with little evidence of gradual decline. 
NITROGEN AND CARBON IN OTHER CLAYS AND DEEP DEPOSITS. 
With reference to this apparently indigenous nitrogen percentage, 
it should here be recorded that some determinations of nitrogen were 
made in the Kothamsted laboratory in L874, in a sample of the Oxford 
•lay obtained in the Snb-Wealden exploration boring at Battle, at a 
depth of from 5^0 to <)< XI feet . This showed, OD an average of four 
closely agreeing analyses, 0.0442 per cent of nitrogen, or very nearly 
the same proportion as that in the lower clay subsoils at Kothamsted. 
Quite recently (June, L900) Sir Henry Gilbert has obtained from 
the geological survey office, by the kindness of Sir Archibald (o-ikie, 
a number of deposits — some of them clayey, and some highly calcare- 
ous — from deep borings, in which he has had determined the nitrogen 
and organic carbon and the ratios of carbon to nitrogen and of nitro- 
gen to carbon. The results are given in the following table: 
[Fable ;>0. — Analyses of deep day deposits compared with average results of deep 
subsoils at Rothamsted. 
[Percentages of carbonate of lime, nitrogen, and organic carbon in fine dry soil: also ratios of 
carl)on to 1 nitrogen, and of nitrogen to 100 carbon.] 
Carbon- 
ate of 
lime. 
Nitrogen 
i mean >. 
Organic 
carbon 
(mean). 
Carbon Nitrogen 
to 1 to 100 
nitrogen, carbon. 
Rothamsted soils, various fields, seventh to 
Per cent. 
Per cent. 
Per cent. 
twelfth depths a 
0.0460 
Oxford clay, Sub- Wealden boring, near Battle, 
Sussex, "/ki -600 feet. .Received in 1874) 
.0442 
Oxford clay. Brabourne bore ^at 1.370 feet). 
West BiWDonrne, Kent 
21.35 
.(US J 
0.786 
16.3 
6.1 
Wealden mottled dav, Brabourne boring at 
r>01 1 feet 

.0343 
.533 
15.0 
6.5 
Gault, Meux's Brewery, Tottenham Court Road 
30. 56 
.0397 
.613 
15.5 
6.5 
London clay, tunnel for Electric Railway. Picca- 
dilly Circus 
731 
.0412 
.391 
9.5 
10.5 
a Deduced from 222 separate samples and 204 nitrogen determinations, made for the most part 
in duplicate, on a mixture of two or more individual samples from each plat or each depth. 
