<p style='text-align: justify;'>Black and white photograph of CTR Wilson's cloud chamber of 1911 before the glass bulb was extended. The rapid expansion of the cloud chamber was synchronised with a 'flash bulb' to take photographs. The first images of the tracks of alpha and beta particles were obtained in 1911 (see P1917). As Blackett (1960) remarked, '(They) still remain among the technically best photographs ever made.' Wilson was awarded the 1927 Nobel Prize in Physics for this work.</p>