A sermon being an incouragement for Protestants : or a happy prospect of glorious success: with exhortations to be valiant against our enemies, in opposing the bloody principle of papists, and errors of popery, &c. Occasionally on the Protestants victory over the French and Irish papists before London-Derry, in raising that desperate siege, a glorious prospect of the Protestants happiness, &c. By Mr. Walker minister, and governor of the city.