_20th._--This day has opened upon me fraught with new cares and responsibilities. This is my twenty-first birth-day. My country can now fairly claim my influence in sustaining her laws, and supporting her institutions. When an American youth enters upon the stage of political life, he should endeavor fully to comprehend the genius of its government, and the high and glorious privileges it imparts. His freedom of thought and right of suffrage place him far above, in point of privilege, any other people, and secure to him blessings not enjoyed by any other nation under heaven. In view of the inestimable rights he enjoys, how great are his obligations! How carefully should he endeavor to avoid party influences; and remain firm in noble principles, in spite of the deluding sophistry of heartless demagogues. As he approaches the ballot-box, that sacred guarantee of liberty when unabused, let him pause and reflect whether he is acting from impulse or the dictates of reason. I am now twenty-one! We all look forward with interest to the period! We expect, and we anticipate, and how often, during the flow of buoyant thought, we map out the way to future greatness. My feelings are so fluctuating, my anticipations so frequently unrealized, that no result can be very unexpected. From this candid and free expression of my feelings, I do not wish to convey the idea that I am disposed to find fault with the world, or with the organization of society, but only to indicate more clearly the constitution of my mind with native sources of unhappiness. In looking back over a few years in which I have mingled some in society, I cannot say I have derived no pleasures from the past, that I have seen no bright spots, or enjoyed no valued objects. It would be base ingratitude were I to disclaim participation in some delightful scenes where sympathy and affection warmed kindred hearts. Was this more than balanced by painful reaction? The frequent brooding upon saddening subjects, pride, and, I may add, a sprinkling of patriotism, will, to some extent, account for this day finding me a soldier upon the borders of Mexico. It is time I should leave this subject. I drop it at once to recount some of the events of the day. Yesterday we were visited by a strong north-wester, so common to the season in this latitude. It blew so hard that the water from the Gulf was driven up into the sloughs, causing a swelling from the little salt lakes of which I have before spoken; but to-day we have a clear sky and a calm breeze. After breakfast this morning, I went to the sutlers, and bought a large box of sardines and some claret, as a little treat for the mess. Our captain and lieutenants were invited to partake, and toasting my birth-day, they all wished me success. I spent the night until tattoo, in writing these random reflections, and in thinking what a contrast the associations of to-day will present, when compared with three preceding anniversaries of my birth-day.