vibrating electrotome with induction coil (missing)
Date1848-1855
Inventory Number0120
ClassificationInduction Coil
Subject
Attributed to
Daniel Davis, Jr.
1813 - 1887
Cultural Region
Place of Origin
Dimensions8.8 × 18.8 × 8.1 cm (3 7/16 × 7 3/8 × 3 3/16 in.)
Material
Bibliography
DescriptionA pair of brass bands, mounted on a mahogany base with four brass ball feet, was used to secure in place the double coil (missing). A small electromagnet made of two coils is mounted at one end of the base, with its keeper attached to a pivoted beam which opened and closed the electrical circuit (the electrotome, which was used as a circuit breaker). Two pairs of brass binding posts are fixed on the base, one (besides the electrotome) to link the instrument to a battery, the other to link the instrument to a pair of handle (which delivered the electric shocks).
This device was sold by Davis between $10.00 and $12.00 dollars in 1848. The electrotome itself was sold between $4.00 and $5.00 that same year.
This device was sold by Davis between $10.00 and $12.00 dollars in 1848. The electrotome itself was sold between $4.00 and $5.00 that same year.
Curatorial RemarksThis device, with the electrotome, does not appear in the 1842 edition of Davis's book on magnetism, but only in the later editions. The use of a rasp as a breaker was introduced by Joseph Henry and Charles Grafton Page ("American Journal of Science," 31 [1836]). This style of electrotome breaker may have been introduced by Page. Only Page's and Davis's double coil and electrotome (with clockwork) is illustrated in Farrar and Lovering volume of 1842.
FunctionUsed in lecture demonstrations and in medicine. The battery was connected across the inner (primary) coil and the vibrating electromagnetic switch (electrotome). When the battery connection was made across the electrotome, high voltage pulses were induced in the outer (secondary) coil, which the patient received by holding a pair of handles connected to the coil's ends.
Davis explains in 1848: "With a battery of even moderate power, the shocks may be made to follow each other with exceeding rapidity. When their strength is lessened considerably by removing nearly all the iron wires from the helices, instead of distinct shocks, a peculiar sensation of numbness is experienced, extending a greater or less distance up the arms, and attended by loss of power over the muscles as far as it reaches. The shocks are never so powerful with a self-acting interruptor as when the circuit is broken mechanically, since the battery current is obliged to maintain the motion of the interruptor as well as to traverse a circuit of greater length."
Davis explains in 1848: "With a battery of even moderate power, the shocks may be made to follow each other with exceeding rapidity. When their strength is lessened considerably by removing nearly all the iron wires from the helices, instead of distinct shocks, a peculiar sensation of numbness is experienced, extending a greater or less distance up the arms, and attended by loss of power over the muscles as far as it reaches. The shocks are never so powerful with a self-acting interruptor as when the circuit is broken mechanically, since the battery current is obliged to maintain the motion of the interruptor as well as to traverse a circuit of greater length."
ProvenanceFrom the Department of Physics, Harvard University.
Daniel Davis, Jr.
Date: circa 1848
Accessories: battery (0566b); pair of shock handles (0566c,d)
Object number: 0566a
Daniel Davis, Jr.
Date: circa 1848
Object number: 1997-1-1801
