Even in respect to New England the evidence is abundant that it was economic rather than moral or religious influences that paved the way to freedom for the slave. At the beginning it was the imperative demand for labor that led to the enslavement of the Indian and Negro, which the Puritan justified by an appeal to his high Calvinism. When this demand ceased because of the increase of white labor and when the diminished supply rendered it more difficult to get profitable slaves, the same economic laws tended to encourage the freedom of the slave.[292] "Fortunately for the moral development of our beloved colonies," says Weeden, "the climate was too harsh, the social system too simple, to engender a good economic employment of black labor. The simple industrial methods of each New England homestead, described in so many ways through these pages, make a natural barrier against an alien social system including either black or copper-colored dependents. The blacks soon dwindled in numbers, or dropped out from a life too severe for any but the hardiest and firmest fibered races."[293] When we see how during the constitutional convention of 1787 selfish economic interests led Massachusetts to enter into the unholy alliance with the pro-slavery States of the far South to fix upon another section of the country the nefarious slave-trade for twenty years longer, we may perhaps conclude that it was after all fortunate for the integrity of the Puritan conscience that slavery was unprofitable as a domestic institution. The slave-trade ended in 1808 and during the years 1806, 1807 six hundred New England slavers arrived at the port of Charleston alone.[294]