Henry Letheby
Encyclopedia
Henry Letheby analytical chemist and public health officer, was born at Plymouth
in 1816, and studied chemistry at the Royal Cornwall Polytechnic Society
. In 1837 he commenced the study of medicine, and became the assistant of Jonathan Pereira
. He graduated M.B. at the University of London
in 1842, and was also LSA (Licentiate of the Society of Apothecaries) (1837) and PhD.
He was lecturer on chemistry at the London Hospital, and for some years medical officer of health and analyst of foods for the City of London. He was also appointed chief examiner of gas for the metropolis under the Board of Trade
. Letheby was an exceedingly accurate technological chemist, and contributed many papers to The Lancet
and other scientific periodicals. He was a fellow of the Linnean Society and the Chemical Society
. He died on 28 March 1876 at his residence, 17 Sussex Place, Regent's Park, London. He left a widow. Letheby's chief work was a treatise on Food, its Varieties, Chemical Composition, &c., London, 1870, 8vo; 2nd edit. 1872. His official reports on the sanitary condition of London were published from time to time.
Letherby designed an interrupter circuit for use with induction coil
s for the medical application of electricity. The function of an interrupter circuit is to continually make and break the supply to the induction coil which causes the coil to generate a large back emf at its output each time it is switched. Early interrupters were operated by hand, but Golding Bird
introduced an automatic interrupter which worked electromagnetically in 1838. The problem with Bird's interrupter, and the problem that Letherby wished to solve, was that the direction of flow of the electric current was in opposite directions during the make and the break operations. Medical applications of electricity often required a unidirectional current, particularly when treating nervous disorders. Lertherby's design caused only either the make or the break current to flow to the patient by a mechanical arrangement of two spoked wheels. Letherby proposed that a further advantage of his machine was that the pulses from the make contact provided a rather lesser shock to the patient than the pulses from the break contact. This gave the physician some control in situation where large shocks were not needed.
Plymouth
Plymouth is a city and unitary authority area on the coast of Devon, England, about south-west of London. It is built between the mouths of the rivers Plym to the east and Tamar to the west, where they join Plymouth Sound...
in 1816, and studied chemistry at the Royal Cornwall Polytechnic Society
Royal Cornwall Polytechnic Society
The Royal Cornwall Polytechnic Society is an educational, cultural and scientific charity, based in Falmouth, Cornwall, England, United Kingdom. The Society exists to promote innovation in the arts and sciences...
. In 1837 he commenced the study of medicine, and became the assistant of Jonathan Pereira
Jonathan Pereira
Jonathan Pereira was a pharmacologist, author of the Elements of Materia Medica, a standard work. He was examiner on the subject in the University of London....
. He graduated M.B. at the University of London
University of London
-20th century:Shortly after 6 Burlington Gardens was vacated, the University went through a period of rapid expansion. Bedford College, Royal Holloway and the London School of Economics all joined in 1900, Regent's Park College, which had affiliated in 1841 became an official divinity school of the...
in 1842, and was also LSA (Licentiate of the Society of Apothecaries) (1837) and PhD.
He was lecturer on chemistry at the London Hospital, and for some years medical officer of health and analyst of foods for the City of London. He was also appointed chief examiner of gas for the metropolis under the Board of Trade
Board of Trade
The Board of Trade is a committee of the Privy Council of the United Kingdom, originating as a committee of inquiry in the 17th century and evolving gradually into a government department with a diverse range of functions...
. Letheby was an exceedingly accurate technological chemist, and contributed many papers to The Lancet
The Lancet
The Lancet is a weekly peer-reviewed general medical journal. It is one of the world's best known, oldest, and most respected general medical journals...
and other scientific periodicals. He was a fellow of the Linnean Society and the Chemical Society
Chemical Society
The Chemical Society was formed in 1841 as a result of increased interest in scientific matters....
. He died on 28 March 1876 at his residence, 17 Sussex Place, Regent's Park, London. He left a widow. Letheby's chief work was a treatise on Food, its Varieties, Chemical Composition, &c., London, 1870, 8vo; 2nd edit. 1872. His official reports on the sanitary condition of London were published from time to time.
Letherby designed an interrupter circuit for use with induction coil
Induction coil
An induction coil or "spark coil" is a type of disruptive discharge coil. It is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current supply...
s for the medical application of electricity. The function of an interrupter circuit is to continually make and break the supply to the induction coil which causes the coil to generate a large back emf at its output each time it is switched. Early interrupters were operated by hand, but Golding Bird
Golding Bird
Golding Bird was a British medical doctor and Fellow of the Royal College of Physicians of London. Bird became a great authority on kidney diseases and published a comprehensive paper on urinary deposits...
introduced an automatic interrupter which worked electromagnetically in 1838. The problem with Bird's interrupter, and the problem that Letherby wished to solve, was that the direction of flow of the electric current was in opposite directions during the make and the break operations. Medical applications of electricity often required a unidirectional current, particularly when treating nervous disorders. Lertherby's design caused only either the make or the break current to flow to the patient by a mechanical arrangement of two spoked wheels. Letherby proposed that a further advantage of his machine was that the pulses from the make contact provided a rather lesser shock to the patient than the pulses from the break contact. This gave the physician some control in situation where large shocks were not needed.