Sir,--Newspapers, and some among your friends, complain of the manner in which many of your constituents are obliged to regard your vote on the Mexican War Bill. This vote is defended with an ardor such as even Truth, Freedom, and Right do not always find in their behalf,--while honest strictures are attributed to personal motives, sometimes to a selfish desire for the place you now hold, sometimes even to a wanton purpose to injure you. All this may be the natural and inevitable incident of political controversy; but it must be regretted that personal feelings and imputations of personal selfishness should intrude into the discussion of an important question of public duty,--I might say, of public morals. As a Whig, never failing to vote for you when I had an opportunity, I have felt it proper on other occasions to review your course, and to express the sorrow it caused. For this I am arraigned; and the question of public morals is forgotten in personal feeling. This is my excuse for recalling attention now to the true issue. Conscious of no feeling to yourself personally, except of good-will, mingled with the recollection of pleasant social intercourse, I refer with pain to your vote, and the apologies for it which have been set up. As one of your constituents, I single you, who are the representative of Boston, among the majority with whom you acted. I am not a politician; and you will pardon me, therefore, if I do not bring your conduct to any test of party or of numbers, to any sliding scale of expediency, to any standard except the rule of Right and Wrong. To understand your course, it will be necessary to consider the action of Congress in declaring war against Mexico. I shall state the facts and conclusions briefly as possible. By virtue of an unconstitutional Act of Congress, in conjunction with the _de facto_ government of Texas, the latter was annexed to the United States some time in the month of December, 1845. If we regard Texas as a province of Mexico, its boundaries must be sought in the geography of that republic. If we regard it as an independent State, they must be determined by the extent of jurisdiction which the State was able to maintain. Now it seems clear that the river Nueces was always recognized by Mexico as the western boundary; and it is undisputed that the State of Texas, since its Declaration of Independence, never exercised any jurisdiction beyond the Nueces. The Act of Annexation could not, therefore, transfer to the United States any title to the region between the Nueces and the Rio Grande. That region belonged to Mexico. _Certainly_ it did not belong to the United States.