4 ideas
The capital works like a heart drawing in provisions from every county, and its appetite decides what distant regions specialize in. Norfolk turkeys and geese are driven on foot to the city, Scottish and Welsh cattle are fattened in the home counties for Smithfield, and coal comes by sea from Newcastle. A single dominant market therefore shapes land use, livestock routes and occupations hundreds of miles away.
Around Halifax, Defoe describes hills covered with scattered houses, many with tenter frames of drying cloth and running water nearby, while coal from pits on the hills is carried to the houses for fuel. The households spin, weave or finish wool, with children also at work, so a barren landscape supports a dense and busy population. Coal, water and the cloth trade close at hand let small household units produce for a wide market without a factory.
The Tour tends to read places by what their trade is doing now rather than by their ancient importance. Dunwich, once a great town, has been largely eaten away by the sea and reduced to a shadow of itself, though Defoe notes it still keeps some trade in butter, cheese and corn, while places tied to thriving trades and ports are growing. In Defoe's reading, a town's present commerce weighs more in its fortunes than its history or charters.
Defoe argues that Britain is changing so fast, with new buildings, shifting trades, towns rising and decaying, that no description of it can stay accurate. Any account is a snapshot that needs constant revising, so a survey of a nation should record flows and changes rather than fixed monuments. That is why the book stresses present commerce over antiquarian description.