MARK TWAIN.-- An immense audience assembled at Wieting Opera House last evening to make the acquaintance of this celebrated humorist. Mr. Clemens's subject was Artemus Ward. His tribute to the genius and untimely end of the genial proprietor of the "great moral wax figgers" had at times a touch of geniune pathos while at the same time it was replete with humorous anecdotes concerning the lamented Artemus and quotations from his writings. Mark resembles the subject of his lecture in one respect -- his pauses are more eloquent than his words. As it is impossible to report a pause, while to leave out these "brilliant flashes of silence" would be to spoil the lecture, we shall not attempt to reproduce it. The audience was quick to see the places where the laugh came in, and responded unanimously. They were not, as the lecturer promised they should not be, loaded down with historic facts to such an extent that they couldn't get home, but all carried with them, we have no doubt, the impression of having had some of the cobwebs shaken out of their brains.