Johann Adam Hoyer was a clockmaker and master craftsman in Josefstadt (now the 8th district of Vienna) who died in 1838.
[1] Hoyer was one of a few clockmakers in the early 19th century who experimented with hydrogen-powered winding mechanisms.
Above the movement is a coiled spiral brass tube holding balls of zinc which, as the driving weight nears its lower position, are released one by one to fall into a solution of dilute sulphuric acid in the red glass jar.
Hydrogen gas is generated and the resulting pressure lifts the entire mechanism behind the dial, winding the going weight, the larger of the two visible.
The smaller weight is used to maintain the clock in motion whilst the larger is wound, the winding process being quite slow.