Summer brought its own pleasures as well as duties. At Lake Calhoun, Lake Harriet, Lake of the Isles, and Minnehaha Falls, many were the picnics held when visitors came to the garrison.[254] Swan, geese, and ducks were numerous about the lakes and swamps, and with the famous hunter H. H. Sibley as a guide, the game bags were soon filled. During a period of three years, Mr. Sibley, alone, shot 1798 ducks--a fact which indicates what success a soldier-sportsman could have in his few hours of recreation.[255] But it was when the prairies were impassable because of drifts of snow from six to fifteen feet high,[256] and when the course of the river could be traced only by a streak of white between the gray of its wooded banks that there appeared those features which are peculiar to the life of a remote garrison. The isolation was almost complete. There was no traffic upon the frozen river, and the traders were wintering in the Indian villages. Only through the mail was communication with the outside world possible. It was planned to have a monthly mail service, soldiers being sent to Prairie du Chien with the letters. Here they delivered about two-thirds of the mail to the persons to whom it was addressed and the rest was deposited in the post office.[257] In summer the mail was carried by the soldiers in canoes, but in winter the journey had to be made on foot. In summer the labor was lightened when a passing steamer overtook the rowing soldiers and picked up the canoe with its crew. In winter no such aid was possible. A hard day's tramp was followed by a night among the drifts, unless the tepee of some friendly Indian gave a temporary respite for a few hours.[258] Nor was this task free from perils. A system was arranged whereby a courier from Fort Snelling and one from Prairie du Chien set out at about the same time, meeting at Wabasha's village where the packs were exchanged and each returned to his own post. On one occasion a spring thaw overtook the carrier from Prairie du Chien, who had proceeded beyond the meeting place because the messenger from the north was late. Suddenly the ice groaned and cracked, and the postman with difficulty found safety on a small island where, to his great surprise, he found the postman from Fort Snelling who had been caught in the same manner. Their provisions soon gave out; for a while they had only rose-apples to eat. It was not until almost two weeks later that the two half-starved messengers were picked up by the canoes of some friendly Sioux.[259]