In 1851 Sitgreaves reconnoitred the country about on the trail of Garces, and in 1854 Whipple, also for the Government, explored along the 35th parallel. The mighty gorges carved through the great plateau prohibited north and south travel, for they were well-nigh impossible to cross except at the one or two places mentioned. A mountain range of equal length and of the greatest magnitude would not have offered so tremendous an obstacle. In 1857 E. F. Beale surveyed a waggon-road along the 35th parallel for the Government, and Johnson, in his steamer, the _General Jesup_, went up from Yuma early in January, 1858, to ferry Beale across on his return from California. Before meeting Beale, Johnson pushed his steamer experimentally on up the river to the head of Black Canyon, the highest point attainable by steamers under the most favourable conditions. He did this to expressly anticipate the exploration planned by Lieutenant Ives, of the Topographical Engineers, who, the month before, December, 1857, had landed at the mouth of the river with sections of a steamboat, _The Explorer_, built in Philadelphia, with which he intended to find the head of navigation and also map the river. Ives conducted this survey with skill and accuracy, and while Johnson's manœuvre took from him the distinction of first ascent, nevertheless he remains the first explorer of the river in this region. He went to the foot of Black Canyon with his steamer and thence to the head of Black Canyon with a small boat. He visited the Grand Canyon at the mouth of Diamond Creek, the Havasupai Canyon, and also the Moki Towns. His report is a model of graceful diction, but many of the illustrations are preposterous. In 1866 Captain Rodgers took the steamer _Esmeralda_, ninety-seven feet long, drawing three and a half feet of water, up to Callville, not far below the mouth of the Virgin.