riddle - separate with a riddle, as grain from chaff screen sift, sieve, strain - separate by passing through a sieve or other straining device to separate out coarser elements; sift the flour
Causing the Civil War. Historically, textbooks have taught that incompatibility between northern and southern economies caused the Civil War. The industrial revolution in the North, during the first few decades of the 19th century, brought about a machine age economy that relied on wage laborers, not slaves.
Northerners did not need slaves for their economy and fought a war to free them. Everything else, many textbooks claim, was tied to that economic difference and was anchored by cotton. The agricultural economy was certainly one cause of the Civil War, but not the only one. Wars are never simple and neither are their causes. Many other factors that helped bring about the war are central to understanding America's past.