Bal′last.
1. (Railroad-engineering.) Gravel, broken stone, or cinders placed beneath and around the sleepers of a railroad track, forming a solid bed which will not retain water. Drainage must be provided below the ballasting. In England, where it is also called metal, twofeet bed of ballast is deemed sufficient, no water being allowed to stand within a depth of four feet below the rails. Ballast has four duties to perform: — a. To distribute the bearing over the surface of the earthwork. b. To confine the track in place. c. To permit drainage of the surface. d. To afford a certain degree of elasticity. A solid rock sub-way is too unyielding, and injures the rolling stock. Burned clay is a fair material. Cinders, shells, and small coal are also used in certain localities.
2. (Nautical.) Weight in the bottom of a boat or the hold of a vessel, to keep it upright in the water, and prevent its being upset by the force of the wind or the weight of its top-hamper. On board vessels of war pig-iron is generally employed for ballast; that of the British navy consists of iron pigs of about 300 pounds each. Means have been provided for using water as ballast. Its evident convenience, both as to accessibility and facility of removal, have induced considerable pains to be incurred in devices for containing it. The employment of water-tight bags has been several times attempted. These, when empty, are stored away in large boxes, and when required are spread out in the hold and filled by a connecting hose. There are evident objections to this mode. Iron tanks have been built into the ship, occupying positions on the floor, and at the stem and stern next to the dead-wood. Tanks made by two bulkheads across the vessel have also been used. These are made of such a size that they may be used for coals or cargo when the ballast is not required. The reservoir, whatever form it may have, must be quite full, to prevent the swashing of the water, and the bulkhead tank has been found difficult to fill and keep tight. The plan suggested by Grantham, of Liverpool, — a distinguished authority on the subject, — is specially adapted for ships carrying coal, where little or no back freight is to be had. See Grantham's “Iron ships,” Weale's Series.
 |
| Ballast car (English form). |
