John Wesley Powell 
First Through the Grand Canyon [PDF ebook] 
Being the Record of the Pioneer Exploration of the Colorado River in 1869-70

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. The Colorado River of the West is formed in southeastern Utah by the junction of the Grand and Green rivers. For hundreds of miles it flows through a series of profound chasms, in many places from 4, 000 to 6, 000 feet deep, and rising nearly vertically for a considerable distance above the water. These canons are from one to fifteen miles wide at the top. The most famous of them is the Marble-Grand canon (really continuous, although it goes under two names, the Marble and the Grand). Through this vast gorge the Colorado drops 2, 330 feet in 283 miles, the current sometimes attaining a velocity of twenty-five miles an hour. The river itself varies in width from seventy-five feet to a quarter of a mile. In the narrowest places it has at times a depth of over 100 feet.