what is the meaning of "heating the tar" here? is it a proverb?
Those humble folk who watched over the new birth—Capron, of Auburn, who first lectured upon it in public; Jervis, the gallant Methodist minister, who cried, "I know it is true, and I will face the frowning world!"; George Willetts, the Quaker; Isaac Post, who called the first spiritual meeting; the gallant band who testified upon the Rochester platform while the rowdies were heating the tar—all of them are destined to live in history.