This section is from the book "Scientific American Reference Book. A Manual for the Office, Household and Shop", by Albert A. Hopkins, A. Russell Bond. Also available from Amazon: Scientific American Reference Book.
The following signals recommended by the late International Marine Conference for adoption by all institutions for saving life from wrecked vessels, have been adopted by the Life-saving Service of the United States.
1. Upon the discovery of a wreck by night, the life-saving force will burn a red pyro,technic light or a red rocket to signify. "You are seen; assistance will be given as soon as possible."
2. A red flag waved on shore by day, or a red light, red rocket, or red Roman candle displayed by night, will signify, "Haul away."
3. A white flag waved on shore by day, or a white light slowly swung back and forth, or a white rocket or white Roman candle fired by night, will signify, "Slack away."
4. Two flags, a white and a red, waved at the same time on shore by day, or two lights, a white and a red, slowly swung at the same time, or a blue pyrotechnic light burned by night, will signify, "Do not attempt to land in your own boats; it is impossible."
5. A man on shore beckoning by day, or two torches burning near together by night, will signify, "This is the best place to land."
 
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