MERCURY IN THE TWELFTH HOUSE, if well aspected gives a mind peculiarly fitted to delve into the mysterious, occult or secret things. This is especially the case if Mercury is between the Sun and Midheaven, that is to say if Mercury goes BEFORE the Sun or rises earlier than that luminary, for then all the light that is in the spirit seems to shine forth and make the person intellectually keen and bright. Therefore this is a good position for detective work as well as scientific or occult research work.
Chemists of great ability have been produced under this aspect for such people have the faculty of going into the most minute details in things which seem microscopic and unimportant to others. When Mercury is in the Twelfth House and afflicted, especially by Saturn or Mars, also when COMBUST or BEHIND THE SUN there is a danger that the mind may become clouded and insanity may result. It may also be noted that the affliction will vary according to the way Mercury is aspected; if by Mars or Uranus the subject may be exceedingly violent, if by Saturn he will become melancholy, but whatever the cause, if Mercury is afflicted in the Twelfth House some form of limitation will restrain the spirit, for the Twelfth House is the house of limitation and confinement.
Deafness is also the result of this position of Mercury when severely afflicted by Saturn.