Wrigley 2

one necessary condition for an expanding economy is increased agricultural production
more details on agricultural technology: http://www.clemson.edu/caah/history/Facultypages/pamMack/lec122sts/Hobsbawm5.html
road transportation was improving: turnpikes were improved roads

Agricultural productivity was increasing rapidly, without increases in the number of people working in agriculture
population doubled, but those people worked in secondary and tertiary industries
agriculture provided not only food but also many industrial raw materials, such as wool and leather
but new energy sources reduce the pressure on limited land

Increase in the use of coal for heat:

Smelting iron with coal:

iron bridge
  the first iron bridge, Coalbrookedale

Growing use of coal required improved transportation on limited routes, justifying more investment in transportation

But what about mechanical energy?
 Watt Engine
The steam engine (more background: http://www.clemson.edu/caah/history/Facultypages/pamMack/lec122sts/Hobsbawm6.html)