Myths and Legends of our Own Land, by Charles M. Skinner, , at sacred-texts.com
The black, pyramidal beacon, called Nix's Mate, is well known to yachtsmen, sailors, and excursionists in Boston harbor. It rises above a shoal,—all that is left of a fair, green island which long ago disappeared in the sea. In 1636 it had an extent of twelve acres, and on its highest point was a gallows where pirates were hanged in chains. One night cries were heard on board of a ship that lay at anchor a little way off shore, and when the watch put off, to see what might be amiss, the captain, named Nix, was found murdered in his bed. There was no direct evidence in the case, and no motive could be assigned for the deed, unless it was the expectancy of promotion on the part of the mate, in case of his commander's death.
It was found, however, that this possibility gave significance to certain acts and sayings of that officer during the voyage, and on circumstantial evidence so slight as this he was convicted and sentenced to death. As he was led to execution he swore that he was not guilty, as he had done before, and from the scaffold he cried aloud, "God, show that I am innocent. Let this island sink and prove to these people that I have never stained my hands with human blood." Soon after the execution of his sentence it was noticed that the surf was going higher on the shore, that certain rocks were no longer uncovered at low tide, and in time the island wasted away. The colonists looked with awe on this manifestation and confessed that God had shown their wrong.