In June, 1763, he "dug up abt. a load of Marle to spread over Wheat Land for experiment." In 1768 he came to the conclusion that most farmers began to cut their wheat too late, for of course cradling was a slow process--scarcely four acres per day per cradler--and if the acreage was large several days must elapse before the last of the grain could be cut, with the result that some of it became so ripe that many of the kernels were shattered out and lost before the straw could be got to the threshing floor. By careful experiments he determined that the grain would not lose perceptibly in size and weight if the wheat were cut comparatively green. In wheat-growing communities the discussion as to this question still rages--extremists on one side will not cut their wheat till it is dead ripe, while those on the other begin to harvest it when it is almost sea-green. In 1763 Washington entered into an agreement with John Carlyle and Robert Adams of Alexandria to sell to them all the wheat he would have to dispose of in the next seven years. The price was to be three shillings and nine pence per bushel, that is, about ninety-one cents. This would not be far from the average price of wheat to-day, but, on the one side, we should bear in mind that ninety-one cents then had much greater purchasing power than now, so that the price was really much greater, and, on the other, that the cost of raising wheat was larger then, owing to lack of self-binders, threshing machines and other labor-saving devices. The wheat thus sold by Washington was to be delivered at the wharf at Alexandria or beside a boat or flat on Four Mile Run Creek. The delivery for 1764 was 257-1/2 bushels; for 1765, 1,112-3/4 bushels; for 1766, 2,331-1/2 bushels; for 1767--a bad year--1,293-1/2 bushels; for 1768, 4,994-1/2 bushels of wheat and 4,304-1/2 bushels of corn; for 1769, 6,241-1/2 bushels of wheat.