The British Isles form a group lying off the north-west coast of Europe, with a total area of about 121,600 square miles (approximately 315,000 sq. km.). The two largest islands are Great Britain proper (comprising the greater parts of England, Wales and Scotland) and Ireland (comprising Northern Ireland and the Republic of Ireland). Off the southern coast of England is the Isle of Wight and off the extreme south-west are the Isles of Scilly; off north Wales is Anglesey. Western Scotland is fringed by numerous islands and to the far north are the important groups of the Orkneys and Shetlands. All these form administrative counties or parts of counties, but the Isle of Man in the heart of the Irish Sea and the Channel Islands between Great Britain and France have a large measure of administrative autonomy and are not part of England, Wales or Scotland.
England (including the county of Monmouth on the Welsh border), with a total area including inland water of 32,558,774 acres (approximately 13,176,000 hectares), is divided into 41 geographical or 50 'civil' counties; Wales, with 4,780,533 acres (approximately 1,935,000 hectares), into 12 counties. Scotland, including its 186 inhabited islands, has a total area of 19,463,016 acres (approximately 7,876,000 hectares), and is divided into 33 counties.
Care must always be taken when studying British statistics to note whether they refer to England as defined above, to England and Wales (considered together for many administrative and other purposes), or to Great Britain which comprises England, Wales and Scotland. The position is further complicated by the fact that the county of Monmouth is sometimes included with Wales. The 'United Kingdom'—formerly the United Kingdom of Great Britain and Ireland, now the United Kingdom of Great Britain and Northern Ireland—is Great Britain with the addition of the six counties of Northern Ireland, 3,488,643 acres (approximately 1,412,000 hectares). Statistics and other data sometimes include but sometimes exclude the Isle of Man, 141,263 acres (approximately 57,000 hectares), and the Channel Islands, off the coast of France, 48,083 acres (approximately 19,000 hectares), which are strictly not part of the United Kingdom. Since southern Ireland became a separate country and independent republic there are now no statistics referring to the British Isles as a whole.
The latitude of 50° North just cuts across the southernmost part of the British mainland (the Lizard Peninsula) and latitude 60° North passes through the Shetland Islands. The northernmost point of the Scottish mainland, Dunnet Head, is in latitude 58° 40′. The prime meridian of o° passes through the old Observatory of Greenwich (London), while the easternmost point of England reaches nearly 1° 45' East and the westernmost point of Ireland is approximately 10° 30′ West. In general terms the British Isles lie mainly within the rectangle 50-60 degrees North and 0-10 degrees West. It is thus rather under 600 miles (966 km.) in a straight line from the south coast of Britain to the extreme north and rather over 300 miles across in the widest part. Owing to the numerous bays and inlets no point in the British Isles is as much as 75 miles from tidal water.
The seas surrounding the British Isles are everywhere shallow—usually less than 50 fathoms or 300 feet (91 metres)—because the islands lie on the continental shelf. To the north-west along the edge of the shelf the sea floor plunges abruptly from 600 feet to 3,000. These shallow waters are important because they provide excellent fishing grounds as well as breeding grounds for the fish. The Gulf Stream, the drift of warm water which
