separable helix (induction) coil
Date1842-1855
Inventory Number0444
ClassificationInduction Coil
Subject
Attributed to
Daniel Davis, Jr.
1813 - 1887
Cultural Region
Place of Origin
Dimensions23.6 × 9.9 × 9.5 cm (9 5/16 × 3 7/8 × 3 3/4 in.)
Material
Bibliography
DescriptionThis coil is made of a simple winding of thin insulated wire. Its two ends connect to a brass screw connector at top and bottom of the coil. The insulated is green. The coil was used in vertical orientation with other parts which are missing.
This design is unusual in that the secondary (outer) and primary (inner) coils were separable from each other, instead of being wound directly over each other, as was done for most subsequent induction coils. Unfortunately, only the outer coil survives in this collection. The inner coil was most likely mounted and fixed on a base, according to Davis's original design.
Davis sold the whole apparatus, with handles for shock, between $12.00 and $18.00 in 1842.
This design is unusual in that the secondary (outer) and primary (inner) coils were separable from each other, instead of being wound directly over each other, as was done for most subsequent induction coils. Unfortunately, only the outer coil survives in this collection. The inner coil was most likely mounted and fixed on a base, according to Davis's original design.
Davis sold the whole apparatus, with handles for shock, between $12.00 and $18.00 in 1842.
Signedunsigned
Curatorial RemarksThis electromagnet served several purposes, as described by Davis in his books of magnetism. It was used in medicine, for example, with shock handles, with or without a clockwork electrotome.
This type of upright coil is also illustrated in Farrar's and Loverings' book (1842), pp. 298-299. The instrument is described as Page's design and illustrated in Joseph Abbot, "Description of Several new Electro-Magnetic and Magnetic-Electric Instruments,'' <i>American Journal of Science</i> 40 (1841): 109.
FunctionFor lecture demonstration in physics as well as medical use. The battery was connected across the missing inner (primary) coil. When the battery connection was interrupted, either by rubbing across a steel rasp (see 0118) or by an electrotome (see 0120), high voltage pulses were induced in the outer (secondary) coil, which the patient received by holding shock handles connected to the outer coil's ends.
ProvenanceFrom the Department of Physics, Jefferson Laboratory, Harvard University.
Daniel Davis, Jr.
Date: circa 1848
Accessories: battery (0566b); pair of shock handles (0566c,d)
Object number: 0566a
Daniel Davis, Jr.
Date: 1848-1855
Object number: 0120
