H. Gr. FORDHAM-HERTFORDSHIRE MAPS. 
9 
as well as the pole of the earth. St. Michael is the largest island 
in the group of the Azores; from its western extremity London 
should he 25° 54' E., the island extending E. and W. between 
25° and 26° W. of Greenwich.* 
This vague western meridian was continued in use, so far as 
British maps were concerned at all events, until towards the end 
of the seventeenth century. In Blome’s ‘ Britannia’ (1673) the 
county maps have no indications of the meridian, hut the map 
of the British Isles which is engraved by Erancis Lamb, and is 
dated 1669, places London at 20° 30' East longitude, which 
is probably based on an initial meridian passing through one of 
the most westerly of the Canaries rather than through the Azores, 
though an accurate measurement would lie between those two 
groups of islands. 
In Seller’s map of Herts (1676) the meridian of London first 
appears. It was from that date uniformly used until about 
the end of the next century, and when fixed more exactly the 
meridian passes through St. Paul’s Cathedral. 
Although the Greenwich Observatory was founded as early as 
1675, it does not appear as the point of the initial meridian of 
longitude until the end of the eighteenth century, the general 
adoption of Greenwich in lieu of London being, no doubt, 
contemporaneous with the triangulation for the Ordnance Survey 
maps, commenced in 1784. Cary’s set of county maps dated 1787 
(with their reprints of later dates) have the meridian of St. Paul’s, 
London, but in his ‘Hew Map of England and Wales, with part 
of Scotland,’ published in sheets, and dated June 11th, 1794, he 
adopts the meridian of Greenwich, and this appears to be the 
earliest map upon which this meridian was used. 
Thus I arrive at three convenient periods for the classification and 
study of our county maps, and I divide my Catalogue accordingly, 
as follows:— 
Part I: 1579-1673 (Saxton to Blome). 
The early and archaic maps : Period of the Dutch School, and 
of the meridian of the Azores or Canaries. 
Part II: 1673-1794 (Seller to Cary). 
The modern and detailed maps, with roads: Period of the English 
School, and of the meridian of London. 
Part III: 1794-1900. 
Period of the Ordnance Survey, and of the meridian of Greenwich. 
I have been at some pains in selecting for the purpose of 
illustration maps and plans representative, so far as possible, of 
the progress of the cartographic art as applied to our county maps 
at different periods. The reproductions have been made by the 
photozincographic process, and are thus exact facsimiles, the 
* See ‘ Encyclopedia Britannica ,’ 9th ed., vol. iii, p. 170, article ‘Azores,’ 
and vol. xvii, pp. 251, 252, and 254, article ‘ Navigation.’ 
