Hamilton argued that the natural faculties of blacks were as good as those of free whites, and he warned that the British would arm the slaves if the patriots did not. In his 21st-century biography, Chernow cites this incident as evidence that Hamilton and Laurens saw the Revolution and the struggle against slavery as inseparable. Hamilton attacked his political opponents as demanding freedom for themselves and refusing to allow it to blacks. In January 1785, Hamilton attended the second meeting of the New York Manumission Society (NYMS). John Jay was president and Hamilton was the first secretary and later became president. Chernow notes how the membership soon included many of Hamilton's friends and associates. Hamilton was a member of the committee of the society that petitioned the legislature to end the slave trade, and that succeeded in passing legislation banning the export of slaves from New York. In the same period, Hamilton felt bound by the rule of law of the time and his law practice facilitated the return of a fugitive slave to Henry Laurens of South Carolina. He opposed the compromise at the 1787 Constitutional Convention by which the federal government could not abolish the slave trade for 20 years, and was disappointed when he lost that argument. Hamilton never supported forced emigration for freed slaves. Horton has argued from this that he would be comfortable with a multiracial society, and that this distinguished him from his contemporaries. In international affairs, he supported Toussaint L'Ouverture's black government in Haiti after the revolt that overthrew French control, as he had supported aid to the slaveowners in 1791--both measures hurt France. Scant evidence has been interpreted by a few to indicate Hamilton may have owned household slaves, as did many wealthy New Yorkers (the evidence for this is indirect; McDonald interprets it as referring to paid employees). 
Was John Jay the first secretary of the New York Manumission Society?
No