Iberville contemplated an exploration of the Red River, thinking it might afford access to the gold and silver mines of New Spain, but abandoned the project owing to the representations of the Indians that the river was unnavigable from the interlaced drift-wood, later known as rafts. He turned his attention to the main river, the Mississippi, and visited the Natchez, a brave and powerful tribe of Indians, whose country delighted his heart as resembling France, and where he planned a city to be called Rosalie (now Natchez), which, however, it was not his fate to ever see take definite form, as it was only built long after his death, in 1714, by his brother Bienville. It was at this time that Le Sueur, sent up the Mississippi by Iberville, discovered the St. Peter River, in Minnesota, and attempting mining operations, later brought back a worthless cargo of green earth. To Iberville's credit, it may be said, he viewed this and many other similar schemes of development with a sceptical and practical eye. Later he sent his brother Bienville across country to explore the Red River, which was done with good success. His priest Montigny was also active in extending the faith, both among the Natchez Indians and in the basin of the Tensas River. Indeed, every effort was made under Iberville's sagacious direction to obtain a knowledge of the possibilities of the country, so that its resources might be properly developed. Iberville returned to France ill with fever, but despite his disease, he displayed extraordinary energy in personally advancing the practical affairs of his new colony. Moreover, he prepared a memoir urging the cession of Pensacola by Spain to France, which nation was to establish forts and arm the Indians along the Mississippi River, whereby the interior of America from the Gulf of Mexico to Canada would be under French domination, save the narrow strip along the Atlantic coast already occupied by England. It was a sagacious scheme which if it had been properly supported by France would have entirely changed the future of America. It received, however, but a perfunctory support, and only resulted in exciting the jealousy of Spain. Iberville's last voyage to Louisiana was made in 1701, when his health, undermined by the climate, was impaired by the formation of an abscess which confined him to his bed for two months. His mind worked incessantly, and his activity through other hands was wonderful. He planned the royal magazines on Dauphine Island, located the new post on Mobile River, told off the relief of workmen for the various enterprises, planned flat-boats for lighters, extended relief to the Spaniards at Vera Cruz, and sent Tonti as an agent to make peace with the Choctaws and Chickasaws and secure them as allies. His sailor's eye was particularly pleased with the magnificent forests of Mobile Bay, where the oaks and pines presented the finest timber for ship-building he had ever seen.