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.
These two parts were the southern states known as Confederacy and Northern states known as Union. The main and the declared cause of the conflict was the issue of abolition of slavery. However there were many other underlying issues adding to the conflicts that resulted in the war.