physical forces, in modern terms, the conservation of energy. In 1842, Grove developed the first fuel cell (which he called the gas voltaic battery), which produced electrical energy by combining hydrogen and oxygen, and described it using his correlation theory. In developing the cell and showing that steam could be disassociated into oxygen and hydrogen, and the process reversed, he was the first person to demonstrate the thermal dissociation of molecules into their constituent atoms. The first demonstration of this effect, he gave privately to Faraday, Gassiot and Edward William Brayley, his scientific editor. His work also led him to early insights into the nature of ionisation. For observations made in Ref., Grove is credited for the discovery of sputtering. In the 1840s, he collaborated with Gassiot at the London Institution on photography and the Daguerreotype and calotype processes. Inspired by his legal practice, he presciently observed: In 1852, he discovered striae, dark bands that occur in electrical breakdown, and investigated their character, presenting his work in an 1858 Bakerian lecture. On the Correlation of Physical Forces In 1846, Grove published On The Correlation of Physical Forces in which he anticipated the general theory of the conservation of energy that was more famously put forward in Hermann von Helmholtz' Über die Erhaltung der Kraft (On the Conservation of Force) published the following year. His 1846 Bakerian lecture relied heavily on his theory. James Prescott Joule had been energized by his investigations into the mechanical equivalent of heat by comparing the mass of coal consumed in a steam engine with the mass of zinc consumed in a Grove battery in performing a common quantity of mechanical work. Grove was certainly familiar with William Thomson's theoretical analysis of Joule's experimental results and Thomson's immature suggestions of conservation of energy. Thomson's public champion, Peter Guthrie Tait was initially a supporter of Grove's ideas but later dismissed them with some coolness. Though Groves's ideas were forerunners of the theory of the conservation of energy, they were qualitative, unlike the quantitative investigations of Joule or Julius Robert von Mayer. His ideas also shaded into broader speculation, such as the nature of Olbers's paradox, which he may have discovered for himself rather than through a direct knowledge. Grove also speculated that other forms of energy were yet to be discovered "as far certain as certain can be of any future event." Royal Society politics As soon