Your favor of the 31st. Ult. was duly recd. You have not mistaken my idea of the Constl. power of Congs. to regulate trade: and it gives me pleasure that you take the same view of it. "The power to regulate trade" is a compound technical phrase, to be expounded by the sense in which it has been usually taken, as shewn by the purposes to wch. it has been usually applied. To interpret it with a strictness excluding whatever is not specified, would exclude even the retaliating & extorting power against the unequal policy of other nations, which is not specified, yet admitted by all to be included. The Custom House has in fact been more generally used as the instrument for establishing & protecting domestic manufactures, than for enforcing a liberality or reciprocity abroad.

You make a very pertinent enquiry as to the object & history of the publication in 1801, by Mr. Pendleton, subscribed "The danger not over. A lapse of nearly thirty years would account for failures of a memory more tenacious than mine. I have certainly no recollections favoring the supposition that it referred to any questions then agitated concerning the Constitutional power of Congs. to encourage manufactures by regulations of trade, and must believe that the passage grew out of the broad & ductile rules of construction advanced by Mr. Hamilton on that & other subjects, and to hypothetical abuses of the power not less oppressive than usurpatious. The Language of Mr. P. shews that his ideas were neither very definite nor very positive.

On what authority it is given out that Mr. Jefferson & myself were associated in the preparation of the piece, I can not divine. For myself, I hold it to be impossible. I do not even remember more than that it excited much attention as coming from such a source. That spirit & style would denote the pen of Mr. P. and of him singly. It is possible that Mr. Jefferson in corresponding with him, might, at that crisis, have exhorted him to take up that weapon in order to kill the Snake that had been scotched, and that not doubting my political sentiments, he might have alluded to me in known friendship with Mr. P. as sure to have the same wish with himself. I have looked over all my correspondence of that Period, with Mr. Jefferson & others with whom it was constant & confidential, without finding a ray of light. If Mr. P. wrote in communion with any one my conjecture would point to his kinsman & Eleve Col. J. Taylor, with whom he was always very intimate, and who had almost an antipathy to federal powers. It is much more probable that he concurred in all the opinions expressed by Mr. Pendleton, than that both Mr Jefferson & myself should have done so in some of them. I will renew the search into my files, and if I make any discovery, will let you know it.

The authority of Mr. Hamilton, I observe, is cited, agst. the power in question. If his language in the Federalist was so intended, which is not probable, he must have changed his opinion at a very early day, as is proved by his official Reports which go into the opposite extreme. Such a change if real, would not indeed, be without his own example. In the Federalist he had so explained the removal from Office as to deny the power to the President. In an Edition of the book at New York, there was a marginal note to the passage "that Mr. H. had changed his view of the Constitution on that point.

Mrs. Rives being now with you Mrs. M. joins in offering cordial regards and good wishes for you both