What are the forms of capital coming from the north which motivate growth in the south?
The North embraced the Industrial Revolution as the 1700's came to a close, and began investing in factories and human labor to produce things that had always been produced on family farms. An industrial society fit the Northeast very well, as the soil, especially in New England, tended to be rocky and thin and farming wasn't nearly as lucrative as moving to the city and taking jobs which paid cash. This demographic change fueled more investment on the part of Northerners, who needed raw materials for the factories. . .and one raw material the North couldn't buy enough of was available only in the South--cotton. The South sold cotton to the North and to Britain, and made a lot of money doing so, but the disadvantage to that was the lack of investment into new technologies in the South, which ultimately cost them the Civil War. The North had factories, which made everything one needed to fight a war, and the North had railroads to move these things. The South had few factories and railroads, and couldn't buy what they needed once Abraham Lincoln blockaded their coast to cut off trade from around the world, especially from Britain.