© Science Museum / Science & Society Picture Library
The larger pyrometer was presented to King George III by Josiah Wedgwood, its inventor, in 1786. Wedgwood developed the instrument to measure the high temperatures used in firing pottery. As porcelain shrinks when fired, the shrinkage of small pieces of porcelain could be used to measure kiln temperature. The pieces were fired and then placed in the gauge. The smaller pyrometer is inscribed 'J. Newman, 122 Regent Street, London', and was produced in 1828-1856.