A galvanometer with a glass cover and a copper plate above coil. Nameplate "Ruhmkorff a Paris", On end of tangent screw shaft: "13", Four binding posts.
In 1825, Leopoldo Nobili (1784-1835), an Italian physicist, introduced a sensitive astatic galvanometer that could detect relatively small electric currents, and that was soon popular with scientists around the world. The Smithsonian purchased this example for use by Joseph Henry, the founding Secretary of the Institution. The "Ruhmkorff a Paris" inscription refers to Heinrich Daniel Ruhmkorff (1803-1877), a German instrument maker who established a shop in Paris in 1855. Reference: Leopoldo Nobili, Leopoldo, "Sur un nouveau galvanomètre présenté à l'Académie des Sciences," Bibliothèque Universelle 29 (1825): 119–125.
Keyed socket for a Mather incandescent lamp, c. 1885. Brass shell with brass key, threaded post connector. Ten brass leaf-springs are spaced around the top of the removable shell to hold a Mather lamp. No extant maker's marks.
An electric motor with counter and magnetic brake. Page magneto motor, with counter attached. Horseshoe magnet, painted red, placed horizontally with a two-coil electromagnet set to rotate at the poles. The magnet is 10 1/2" long and 4 1/2" wide. A copper disk, 5 1/2" in diameter is mounted on the base, and apparently is to be driven by the motor. This may be some form of Arago's disc, adjustable on its base. No manufacturer's name is apparent on the specimen. The counter determines armature revolutions. Reference: Davis Manual of Magnetism (Boston, 1869) page 212 for magnet & armature construction. The counter mechanism appears modern.
X-ray Tube, marked: "P1B1", "Waite & Bartlett Mfg. Co. / New York" on cathode. Long cylindrical stem flares into a 3" diameter elongated glass sphere. Unit contains concave metal cathode and square anode. A metal cross-piece between the two extension tubes has broken off on one side.
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
This unusual looking relay bears the stamp of Charles T. Chester of New York. Charles and his brother John ran a business manufacturing electrical devices from 1855 to the latter's death in 1871. Charles patented several devices including improvements for batteries however we have not been able to associate a patent with this relay. The unit itself is a production piece with serial number 326.