Manuscript, 'An account of experiments made with the view of ascertaining the possibility of obtaining a spark before the current of the voltaic battery is completed' by J P [John Peter] Gassiot Gassiot describes how a spark invariably appears when the circuit of the voltaic battery is completed; an effect which Dr [Michael] Faraday has shown can be easily produced, even with a single series. He then refers to the experiments of Mr [John George] Children, Sir Humphry Davy, and Professor [John Frederic] Daniell, recorded in the Philosophical Transactions; in which experiments, when more powerful and extended series were used, the spark was obtained before contact took place. Gassiot explains how a micrometer-electrometer can be used to ascertain not only the fact of a spark being obtained, but also the distance through which it may be passed. He describes the micrometer-electrometer and relates several experiments which he made with a view to test its functionality and accuracy. Followed by a note, dated 19 November 1839, outlining new research he has discovered on the topic of electricity by a Dr Henry. Annotations in pencil throughout. Subject: Physics / Electricity Received 11 October 1839. Read 19 December 1839. Communicated by P M [Peter Mark] Roget. Written by Gassiot at Clapham Common [London]. Published in Philosophical Transactions as 'An account of experiments made with the view of ascertaining the possibility of obtaining a spark before the circuit of the voltaic battery is completed'. 25 August 1839