Gradually the clearings became larger and the area sown increased in size. The trails were improved and took on the semblance of roads, but the waterways continued to be the principal avenues of communication. In each of the four districts the government erected mills to grind the grain for the settlers. These were known as the King's Mills. Water-power mills were located near Kingston, at Gananoque, at Napanee, and on the Niagara River. The mill on the Detroit was run by wind power. An important event in the early years was when the head of the family set out for the mill with his bag of wheat on his back or in his canoe, and returned in two or three days, perhaps in a week, with a small supply of flour. In the early days there was no wheat for export. The question then may be asked, was there anything to market? Yes; as the development went on, the settlers found a market for two surplus products, timber and potash. The larger pine trees were hewn into timber and floated down the streams to some convenient point where they were collected into rafts, which were taken down the St Lawrence to Montreal and Quebec. Black salt or crude potash was obtained by concentrating the ashes that resulted from burning the brush and trees that were not suitable for timber. For the first thirty years of the new settlements the chief concern of the people was the clearing of their land, the increasing of their field crops, and the improving of their homes and furnishings. It was slow going, and had it not been for government assistance, progress, and even maintenance of life, would have been impossible. That was the heroic age of Upper Canada, the period of foundation-laying in the province. Farming was the main occupation, and men, women, and children shared the burdens in the forest, in the field, and in the home. Roads were few and poorly built, except the three great military roads planned by Lieutenant-Governor Simcoe running east, west, and north from the town of York. Social intercourse was of a limited nature. Here and there a school was formed when a competent teacher could be secured. Church services were held once a month, on which occasions the missionary preacher rode into the district on horseback. Perhaps once or twice in the summer the weary postman, with his pack on his back, arrived at the isolated farmhouse to leave a letter, on which heavy toll had to be collected.