The command of another expedition was given in 1828 to Major Long, whose services were thoroughly appreciated. Leaving Philadelphia in April, he embarked on the Ohio, and crossed the state of the same name, and those of Indiana and Illinois. Having reached the Mississippi, he ascended that river to the mouth of the St. Peter, formerly visited by Carver, and later by Baron La Hontan. Long followed the St. Peter to its source, passing Crooked Lake and reaching Lake Winnipeg, whence he explored the river of the same name, obtained a sight of the Lake of the Woods and Rainy Lake, and arrived at the plateau which separates the Hudson's Bay valley from that of the St. Lawrence. Lastly, he went to Lake Superior by way of Cold Water Lake and Dog River. Although all these districts had been constantly traversed by Canadian pathfinders, trappers, and hunters for many years previously, it was the first time an official expedition had visited them with a view to the laying down of a map. The explorers were struck with the beauty of the neighbourhood watered by the Winnipeg. That river, whose course is frequently broken by picturesque rapids and waterfalls, flows between two perpendicular granite walls crowned with verdure. The beauty of the scenery, succeeding as it did to the monotony of the plains and savannahs they had previously traversed, filled the explorers with admiration. The exploration of the Mississippi, which had been neglected since Pike's expedition, was resumed in 1820 by General Cass, Governor of Michigan. Leaving Detroit at the end of May with twenty men trained to the work of pathfinders, he reached the Upper Mississippi, after visiting Lakes Huron, Superior, and Sandy. His exhausted escort halted to rest whilst he continued the examination of the river in a canoe. For 150 miles the course of the Mississippi is rapid and uninterrupted, but beyond that distance begins a series of rapids extending over twelve miles to the Peckgama Falls. Above this cataract the stream, now far less rapid, winds through vast savannahs to Leech Lake. Having reached Lake Winnipeg, Cass arrived on the 21st July at a new lake, to which he gave his own name, but he did not care to push on further with his small party of men and inadequate supply of provisions and ammunition. The source of the Mississippi had been approached, but not reached. The general opinion was that the river took its rise in a small sheet of water known as Deer Lake, sixty miles from Cass Lake. Not until 1832, however, when General Cass was Secretary of State for war, was this important problem solved. The command of an expedition was then given to a traveller named Schoolcraft, who had in the previous year explored the Chippeway country, north-west of Lake Superior. His party consisted of six soldiers, an officer qualified to conduct hydrographic surveys, a surgeon, a geologist, an interpreter, and a missionary.