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The derived classes provided strata. Previous years samples were
ascribed, by location, to particular strata, and the selection of sites
in London Midland Region (Chapter 3) was based, proportionally, on the
derived divisions.
2.3 Results
2.3.1 Track mileage
Of the 1127 ten-mile rail units recognised, 899 were considered rural
(giving an approximate length of 9000 miles) and were scored for the
purposes of this investigation. From previous estimates of British
Rail acreage (Messenger 1968; Way & Sheail 1977), it can be calculated
. that land associated with rural lines (but not including the track)
occupies some 146 000 acres (± 34 000), whilst urban holdings account -
for 37 500 acres (t 14 000).*
2.3.2 Classification
The classification derived from ISA has been mapped (Map 1, cover pocket),
and the dichotomies through which it was obtained are given.
Amalgamation to produce statistically compatible terminal groups led to
a total of 25 stratification classes (Table 2.1, Map 1). Preferential
attributes have been defined for the classes and are tabulated (Table
2.2) with respect to the first axis of Reciprocal Averaging Ordination
(Hill 1973). They suggest the importance of particular climatic and
geological characters in the classification and indicate relationships
between geographically disparate classes.
The initial division of the ISA separated southern, midland and coastal
railway lines, from those occurring in the wetter, colder upland areas
of the north and west. On the negative (southern) side of the
dichotomy, mesozoic and more recent rocks including chalk and oolites,
together with the absence of glacial drift, were important; palaeozoic,
igneous and intrusive rocks were preferential on the positive side.
Soil, altitude and climatic attributes separated in.an expected manner,
about the basic north:south dichotomy; railway type and adjacent land.
use characters were not particularly relevant at this level of division.
At the next stage, the selected attributes separated lines in the
Midlands and East Anglia from those covering the greater part of
southern England; differentiation was also made between the high
igneous and metamorphic areas of Scotland, England and Wales, and the
milder more lowland parts of the north. Subsequent division continued
and defined these trends, with local rather than regional, attributes
playing an increasingly important role.
When field work is.completed and measured widths available for sites
in.all regions, it will become possible to give a more precise
estimate of acreage.
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