Thomas Fowler (inventor)

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Thomas Fowler (born 1777 in Great Torrington, Devon, England – died March 31, 1843) was an English inventor whose most notable invention was the thermosiphon which formed the basis of early hot water central heating systems.

Much of the knowledge of Fowler comes from his son, the Reverend Hugh Fowler, who produced a biography of his father.



Fowler patented the thermosiphon in 1828 (British patent number 5711). It was the first convective heating system. A system based on his design was installed at Bicton, part of the Rolle Estate and received great acclaim in the Gardener's Magazine of 1829. Unfortunately due to innate flaws in the patent system of the time (under which a new version of a design with minimal changes was not covered by the original patent), the thermosiphon was pirated by numerous other manufacturers and Fowler did not have sufficient funds to conduct legal proceedings.

Heating at this time was by means of coal-fired stoves. In large houses these would be placed in a basement, allowing thermosiphon circulation throughout the house. Nearly a century after Fowler, British practice for typical small houses in the post-World War I period developed the back boiler, where a living room fireplace would also have a simple tank boiler built into it. Large diameter pipes from this boiler circulated through a coil heat exchanger in an indirect hot water storage cylinder upstairs. This hot water supplied both bathroom, increasingly fitted upstairs in houses of this period, and the kitchen or scullery downstairs. The height difference between boiler and storage allowed thermosiphon circulation in this simple large bore primary circuit. By the 1960s, the space heating circulation system was assisted by an electric pump. Switching from coal heating to gas boilers also drove a switch to reliable pumped circulation in the 1970s. With the disappearance of stored hot water in favour of the combi boiler, from the 1980s onwards, the thermosiphon disappeared from British plumbing.

Calculating machine[edit]

In 1840 Fowler produced a mechanical calculating machine which operated using balanced ternary arithmetic. Apprehensive in case his ideas should again be stolen, he designed and built the machine single-handed from wood in the workshop attached to his printing business. To compensate for the limited precision achievable using wooden components, he constructed the machine on a large scale; it was 6 feet long by 3 feet deep and 1 foot high (1800 x 900 x 300 mm).

Fowler had previously developed methods using balanced ternary arithmetic to simplify the complex monetary calculations he was obliged to perform on behalf of the Torrington Poor Law Union in his capacity as its treasurer, which he later published in his book Tables for Facilitating Arithmetical Calculations. His machine was designed to give mechanical form to these techniques, the choice of balanced ternary allowing the mechanisms to be simple, though the values had to be converted to balanced ternary before processing and the results converted back to decimal at the end of the calculation.

Though the machine did not survive to the present day, a replica has been constructed from a two-page description of it made in 1840 by the prominent mathematician Augustus DeMorgan.[1] This replica resides at the Science Museum in London.


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