When it is necessary to know the depth of the water at any point in the river, the test or sounding is made by dropping a 33 foot rope, to the end of which is
fastened a pipe filled with lead. The pipe is about one and a half inches in diameter and twelve inches in length. A few inches of heavy chain are put into the pipe, and around this melted lead is poured. The weight of a lead is between six and ten pounds. The rope is fastened to a link of the chain that is allowed to extend past the length of the pipe. The length of the lead line is marked at four feet by a piece of white flannel woven into the rope, at six feet, by a piece of leather, at nine feet by a piece of red cloth; at Mark Twain there is a piece of leather split into two thongs and at Mark Four there is a single leather strip with a round hole. These signals are recognized by the leadsman as the rope slips through his hands in the darkness.
The sounds are called out as the line drops. A depth less than Quarter Less Twain is given in feet. After Mark Four is reached the measurement is usually give as No Bottom.