midnight
Those who had occasion to pass the house frequently after dark perceived that the smoke from this chimney was different from the common smoke of common chimneys . Sometimes vivid sparks glittered and flashed upon the darkness . At other times a semi-luminous , green vapour was seen to issue from the mouth of the chimney . These facts were spoken about by the neighbours ; and by and by people discovered that the smoke issued from the chimney of Victor Carrington 's laboratory , where the surgeon was frequently employed , long after midnight , making experiments in the science of chemistry . The nature of these experiments was known to no one . The few neighbours who had ever conversed with the French surgeon had heard him declare that he was a student of the mysteries of electricity . It was , therefore , supposed that all his experiments were in some manner connected with that wondrous science .