Herbert Darling Foster 
Webster’s Seventh of March Speech and the Secession Movement, 1850 [PDF ebook] 

Detailed article about a speech delivered by Daniel Webster in 1850.
An excellent short work of revision rehabilitating Daniel Webster from progressive historians in the late nineteenth century who accused the Massachusetts senator of selling out liberty to the South for the sake of Union. The chief slanderers were Hermann Van Holst and Henry Cabot Lodge. Foster is correct in his presumption of moral rectitude of Webster. Worth a read for those who believe the "Webster was unprincipled" school of thought.