Model of Robert Duncan's screw propeller, with stern frame and rudder, as fitted to the Egyptian government yacht 'Sareea 1886-1887
Filings coherer, glass tube formed into T-shape at one end and bent round into U-shape at other end with bulb, 1899 1899
Filings coherer, small glass tube with bulb at one end and cap of red sealing wax at other end, 1898 1898