Sir Humphry Davy, English chemist, c 1824.
© Science Museum / Science & Society Picture Library
Engraving by Hodgson. Whilst at the Pneumatic Institute in Bristol, Davy (1778-1829) discovered the anaesthetic effects of laughing gas (nitrous oxide). In 1801, he was appointed lecturer at the Royal Institution, where he isolated the metals barium, calcium, magnesium, potasium, sodium and strontium, but it is his invention in 1815 of the miners' safety lamp (which enabled deeper, more gaseous seams to be mined without risk of explosion) for which he is perhaps best known. Published in 1824.