Demonstration model Astatic Needle Galvanometer with two green insulated coils,
Datecirca 1850
Inventory Number0106
ClassificationAstatic Galvanometer
Subject
Maker
Daniel Davis, Jr. & E. B. Horn
founded c. 1839
Place of Origin
Dimensions14.3 × 15 × 28 cm (5 5/8 × 5 7/8 × 11 in.)
Material
DescriptionA pair of coils of 5 layers of fine wire, insulated in thread and painted green, is mounted on a wood base. The coils are compressed so that their opening is a narrow rectangular slot. The active needle would have been pivoted to move within this slot; the indicator needle would have been positioned above it, so that its deflection angle could have been read against the dial. The many close windings of the fine wire coil allow for detection of small currents. This instrument was used to demonstrate the electricity produced when heat of a flame is applied to a junction of dissimilar metals.
SignedManufactured\ BY\ DAVIS & HORN,\BOSTON.
InscribedOn a plaque between the brass binding posts: "Manufactured By DAVIS & HORN BOSTON"
Curatorial Remarksdial and needle missing from Physics Ref Davis, Daniel Jr Manual of Magnetism (Boston , 1855) p. 69, fig 39 revised by A.G. 7/29/97
FunctionDetects small electrical currents and allows comparison of the strength of the current passing through the coil. This instrument was used to demonstrate the current generated at a thermoelectric junction (missing).
Historical AttributesThe instrument is illustrated in figure 39, p 68-71 in Davis' Manual (1848, 1855, 1869).
L. E. Knott Apparatus Company
Date: circa 1910
Object number: 0451
Robert G. Brown
Date: circa 1884
Accessories: exchange jacknife switch (8035a)
Object number: 8035b
