Unpublished paper, 'On the application of a new principle in the construction of voltaic batteries by means of which an equally powerful current may be sustained for any period required with a description of a sustaining battery recently exhibited at the Royal Institution' by Frederick William Mullins Mullins shares how a continuous voltaic current of equal intensity is obtained through placing a thin membrane between the two metals in the voltaic circuit. This allows the separation of the different fluids applied respectively to each metal: the fluid in contact with the zinc being a mixture of diluted sulphuric and nitric acids and that in contact with the copper being a solution of copper sulphate. Marked on back as 'archives'. Subject: Physics / Electricity Received 19 May 1836. Read 16 June 1836. Communicated by N A [Nicholas Aylward] Vigors. Written by Mullins in London. Whilst the Royal Society declined to publish this paper in full, an abstract of the paper was published in volume 3 of Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London [later Proceedings of the Royal Society] as 'On the application of a new Principle in the construction of voltaic batteries, by means of which an equally powerful current may be sustained for any period required; with a description of a sustaining battery recently exhibited at the Royal Institution'. 9 May 1836