“I scarcely express myself too strongly in saying, that any allusion in the Convention to the subject you have so much at heart would have been a spark to a mass of gunpowder.”

Letter to Lafayette (1 February 1830), published in Letters and Other Writings of James Madison (1867), Vol. IV, p. 60 https://books.google.com/books?id=ugpFAQAAMAAJ&pg=PA60#v=twopage&q&f=false<!-- also quoted in The Last of the Fathers: James Madison and the Republican Legacy (1989), by Drew R. McCoy, Cambridge University Press, p. 252 -->
1830s
Context: Your anticipations with regard to the slavery among us were the natural offspring of your just principles and laudable sympathies; but I am sorry to say that the occasion which led to them proved to be little fitted for the slightest interposition on that subject. A sensibility, morbid in the highest degree, was never more awakened among those who have the largest stake in that species of interest, and the most violent against any governmental movement in relation to it. The excitability at the moment, happened, also, to be not a little augmented by party questions between the South and the North, and the efforts used to make the circumstance common to the former a sympathetic bond of co-operation. I scarcely express myself too strongly in saying, that any allusion in the Convention to the subject you have so much at heart would have been a spark to a mass of gunpowder. It is certain, nevertheless, that time, the “great Innovator,” is not idle in its salutary preparations. The Colonization Society are becoming more and more one of its agents. Outlets for the freed blacks are alone wanted for a rapid erasure of the blot from our Republican character.