Ice

In high latitudes, during the winter, rivers are frequently covered with ice of sufficient thickne to sustain the heaviest loads. This means of communication should be used with great circumspection. A change of temperature may not only suddenly destroy this natural bridge, but render the river impa able by any method for a considerable time in consequence of the floating ice. The thickne of ice should be, to allow the pa age of infantry in single file on a line of planks, and 2 yards apart, 2 inches; cavalry or light guns, with intervals, 4 inches; 12-pounder field-pieces, unlimbered and on sleds, 5 inches; 12-pounder field-pieces, limbered and drawn by horses, with intervals between pieces, 6 to 7 inches. Ice when 10 to 12 inches thick bears the heaviest loads. Two tracks of planks laid on the ice for the carriage-wheels to run on, may be employed when there is any doubt as to its strength, or the wagon may be transformed into a sort of sled by fastening two planks under the wheels. The thickne of the ice may be increased, when the temperature is low enough, by throwing water on it. When the river is frozen on each side, but open in the middle in consequence of the velocity of the current, a boom stretched acro the open space will often check the velocity sufficiently to cause the water to freeze.