"MARK TWAIN'S" LECTURE LAST NIGHT.--The lecture-room of the Mercantile Library Building was well filled with admirers of "Mark Twain" (Mr. Samuel L. Clemens), to hear his lecture on "The Oldest of the Republics--Venice: Past and Present." At a few minutes after eight o'clock (the hour announced for "the orgies" to commence,) the lecturer stepped out from a side door, advanced to the front of the platform, looked around anxiously for a few seconds, and then made the following preliminary remarks:

"Ladies and Gentlemen: If any one in San Francisco has a just right this evening to feel gratified--more, to feel proud--it is I, who stand before you. The compliment of your attendance here I thoroughly appreciate. It is a greater compliment than I really deserve, perhaps--but for that matter I have always been rather better treated in San Francisco than I actually deserved. I am willing to say that. I appreciate your attendance here to-night all the more because there was such a wide-spread, such a furious, such a determined opposition to my lecturing upon this occasion. [Laughter.] Pretty much the entire community wrote petitions imploring me not to lecture--to forbear--to have compassion upon a persecuted people. [Laughter.] I have never had such a unanimous call to--to--to leave, before. [Great laughter.] But I resisted, and am here; and I am glad that I am privileged to address a full house, instead of having to pour out this cataract of wisdom upon empty benches. [Applause.] I do not exactly propose to instruct you this evening, but rather to tell you a good many things which you have known very well before, no doubt, but which may have grown dim in your memories--for the multifarious duties and annoyances of daily life are apt to drive from our minds a large part of what we learn, and that knowledge is of little use which we cannot recall. So I simply propose to refresh your memories. I trust this will be considered sufficient apology for making this lecture somewhat didactic. I don't know what didactic means, [laughter] but it is a good, high-sounding word, and I wish to use it, meaning no harm whatever."

He then gave a sort of compressed history of Venice, the youngest of the Italian cities, and contrasted it in its palmy times with the Venice of to-day, as seen in the glare of sunlight, and not in the charitable rays of the moon--likened it to Sacramento when overflowed; stripped the romance from the gondola (a canoe with a hearse body) and the gondolier; pictured the ladies going shopping, the lover slyly stealing up to the old man's house, the merchant going to his counting-room--all in gondolas, making the place a paradise for cripples. The lecture was interspersed with humorous allusions, anecdotes, and sarcastic allusions to the Americans abroad who affect foreign airs and especially to the dilletanti, but wound up with a burst of glowing rhetoric on the city which is yearly wedded to the sea by solemn ceremonies. The applause was frequent and appreciative throughout the lecture, which lasted one hour and fifty minutes, though it was not a minute too long. Mr. Clemens leaves for the East on Monday, and may be proud to leave with such a tribute to his popularity as the attendance of last night.

MARK TWAIN LAST NIGHT.--Mark's lecture on "Venice" at the Mercantile Library Hall last night was greeted by a full house, composed of the aristocratic and elite of the city, who were quite liberal in their applause of the many good and "telling" points. The lecture was a perfect success both in a literary and financial point of view; it deserves and will no doubt have a successful run in the Atlantic cities.