A hand-held heliostat, comprising two brass tubes, one containing a lens, and a rotating mirror. It is contained in a lined, leather case. The maker's name is inscribed on the body as is 'HO' with a government broad arrow, indicating that it came from the Hydrographic Office (who bought it in 1881). The name of another firm, Elliott Brothers, appears inside the lid of the case.

The instrument was designed in the late 1850s by Francis Galton (1822-1911), who described it to the British Association in 1858 and the Geographical Society in 1860. Galton intended it to be used by travellers to signal across long distances, either on land or at sea, by use of the sun's refelection. It works by sighting the sun through one tube (which has an opaque filter in it), and then moving the mirror to view the target (such as another person) and then flashing them by moving the mirror back and forth.