Carol written in 1818 by Josef Mohr?

That is not correct. The poem "Silent Night" was written in 1818 by Joseph Mohr, a Roman Catholic priest from Austria, not Carol. Mohr was inspired to write the poem on Christmas Eve 1818, while serving as an assistant priest in the small town of Oberndorf bei Salzburg, Austria. The poem was originally written in German, and was later translated into English in the mid-19th century.