This is a rare musical
instrument with its original glasses. These were filled
with water and played by rubbing a finger on the glass’s
outer rim. Different size glasses produced different
notes. This is a labeled example, see the
label attached to the inside of the top. Also,
there is a related example by the same maker owned
by the Maryland Historical Society and illustrated
in Furniture in Maryland, 1740-1940, item 114
(see
scan).
The cabinetry is
also superb, and this piece is attributed to the cabinetshop
of Needles or Barry. Note the Needles style heavy
reeded saber leg and beautifully carved paw feet (see
detail).

A popular Youtube video shows how an accomplished musician (or two) can use this instrument. 
Sugar Plum Fairy by P.Tchaikovsky – Glass Harp LIVE

Height:
37 1/2 in. Width: 36 in. Depth: 23 in.