399. Whoever causes the destruction of any property, or any such change in any property, or in the situation of any property, as destroys or diminishes the value of such property, intending thereby to cause wrongful loss to any party, is said, except in the case hereinafter excepted, to commit “mischief.”
Explanation. A person may commit mischief on his own property.
Exception. Nothing is mischief which a person does openly, and with the intention in good faith of thereby saving any person from death or hurt, or of thereby preventing a greater loss of property than that which he occasions….
The book gives several pages of examples of what was to be considered mischief, and what was not.