Lt.-Col. William Watson, C. M. G., D. Sc., A. R. C. S., Professor of Physics at the Imperial College of Science, London, Director of the Central Laboratory of the British Expeditionary Force in France, from its foundation in 1915 to the end of the war, died in hospital from the results of gas-poisoning on March 3, 1919. Watson was born in 1868, and educated at King’s College School. He received his training in the accurate and delicate physical manipulation which distinguished all his work, at the Royal College of Science under Sir Arthur Rücker and Prof. C. V. Boys, and took his B. Sc. degree in 1890, securing first place on the list of honours in physics. He obtained an immediate appointment as Demonstrator in the Physics Department of the Royal College of Science, and afterwards succeeded to the Assistant Professorship of Physics in 1897. He was elected a Fellow of the Royal Society in 1901, and became in due course one of the Professors of Physics at the Imperial College of Science.