The C.T.R. Wilson Experiment for showing paths of ions. The smallest particles of positive electricity. Charles Thomson Rees Wilson (February 14, 1869 - November 15, 1959) was a Scottish physicist and meteorologist. In 1893 he began to study clouds and their properties. He worked for some time at the observatory on Ben Nevis, where he made observations of cloud formation. He then tried to reproduce this effect on a smaller scale at the Cavendish Laboratory in Cambridge, expanding humid air within a sealed container. He later experimented with the creation of cloud trails in his chamber caused by ions and radiation. For the invention of the cloud chamber he received the Nobel Prize in 1927. The cloud chamber is a particle detector used for detecting ionizing radiation. Cloud chambers played a prominent role in the experimental particle physics from the 1920s to the 1950s, until the advent of the bubble chamber. The gentlemen in the image are not identified, no photographer was credited, dated August 7, 1924.