24 THE ESSEX NATURALIST
only 23/4 inches; the mean of the two results was adopted as the
true measurement. Later again, further baselines were laid
down in various districts. These, however, were at first intended
for military and later for scientific purposes; the idea of maps
of the entire kingdom for general topographical use was of later
growth; the very title "Ordnance Survey" confirms this.
The first Ordnance map issued was of Kent, with the east part
of London and south part of Essex, 1in. to the mile, in four sheets;
it was published by W. Faden on 1st January, 1801. The next
county to be mapped was Essex, published 18th April, 1805, by
Lt.-Col. Mudge. It is in four sheets, each about 23in. by 35in.,
and having as title "Part the First of the General Survey of
England and Wales."
The triangulation of the United Kingdom was not completed
until 1852, and until the Ordnance Survey edition of 1862
appeared no parish boundaries were shown on any Essex map.
Contours were not shown until 1892, hachures being employed
for hill-shading earlier.
Many excellent maps were issued by various publishers during
the 19th century, but these, however good, are necessarily over-
shadowed by the Government maps, which are facile princeps.
Today, the many additions and improvements on the Ord-
nance maps have produced such a state of perfection that they
may be accepted as absolutely reliable; those who have best
learnt how to extract from them their detailed information know
best how wonderfully accurate and informative they are. It is
officially stated that, as a check on the field examiner, errors
were intentionally made on the tracing supplied to him; if he
failed to detect them he got into trouble.
It is said that if the 700 miles between Shetland and Dover
were re-measured with every modern refinement, the difference
between the older and the new measurements would scarcely
be more than 25 yards.
A later development of Governmental mapping was the
Geological Survey Maps, begun in 1835, and founded upon the
maps already issued by the Ordnance Survey authorities. These
also, especially in their recent issues, are full of information, and
the solid "country" rocks, as well as the drift gravels overlying
them, are both indicated on the one map.
It is of interest to know that the meridian of Greenwich,
now universally adopted, is first shown on a map of England and
Wales published by John Cary in 1794. Before that date St.
Paul's Cathedral, London, was used as the meridian from 1676
onwards, while, still earlier, the Azores or some vague point in
the Atlantic was chosen.
Col. Sir Chas. Close (himself a former Director-General of