Rockets.
When approved rockets are used instead of guns, there shall be in every case at least three of said rockets, and all steamers that are required under the law to carry line-carrying projectiles and the means of propelling them shall be supplied auxiliary thereto with at least 800 feet of 3-inch manila line for vessels of over 150 and not over 500 gross tons and 1,500 feet of said line for steamers above 500 gross tons; and, except where approved rockets are provided, with three approved service projectile lines and three projectiles. Such auxiliary line and all other equipment shall be kept always ready for use in connection with the gun and rocket, which lines and other equipment shall not be used for any other purpose. (R. S., 4488.)