Under favorable circumstances infantry can ford a stream where the depth is not greater than four feet; cavalry to a depth of four or five feet; but artillery, and engineer trains, cannot go to a depth of more than two and a half feet, without greatly exposing their ammunition and military stores The fords should be accurately staked out before the passage is attempted, and ropes ought to be stretched across the stream, or cavalry and small boats stationed below, to prevent the loss of life.
Ice may be crossed by infantry, in small detachments.

Its strength may be increased by covering it with boards, or straw, so as to distribute the weight over a greater surface.

By sprinkling water over the straw, and allowing it to freeze, the mass may be made still more compact.

But large bodies of cavalry, and heavy artillery, cannot venture on the ice unless it be of great thickness and strength.

An army can never trust, for any length of time, to either fords or ice; if it did a freshet or a thaw would place it in a most critical state.