Firearms and Fire-works. § 7. No person shall sell to any child under the age of fifteen years, without the written consent of a parent or guardian of such child, any cartridge or fixed ammunition of which any fulminate is a component part, or any gun, pistol or other mechanical contrivance arranged for the explosion of such cartridge or of any fulminate. § 8. Every person violating the provisions of the foregoing section shall be fined not less than ten dollars nor more than twenty dollars for each offence.