..... "…..specifically adapted for use in mines…..".. Coming from a coal mining region, John Hale from Scranton Pennsylvania must have been familiar with mining surveying. Over the years of marketing during the 19th century, Hale's instrument went through variations for use above and below ground, including: full and half circle instruments with and without magnetic compasses, and a rotatable full and half, length arm. This particular example is one of the earlier design semi-circles; possibly a second variation with a full length arm.
The instrument is complete with the original specialized ball & socket leveling mount with a cut-out in the socket which allows the instrument to be used for both horizontal and vertical observations/readings (see images). The instrument was once retrofit with a non-original accessory attachment of which the mount holes are still present on either side of the pivot. The arm is fit with the original bubble vial with multiple position viewing holes which would allow it's use in both horizontal and vertical positions (see images). The glass vial is original and working. The instrument has a nice fitting tripod (marked K&E), which has a proper taper to fit the socket. A plumb bob is lacking.
A rare American patent mine surveying instrument in very good condition, complete with original finish, leveling head, case and tripod.