"the most original and wonderful instrument in scientific history" -Ernest Rutherford

Charles T.R. Wilson's invention of the cloud chamber,
critical in the development of particle physics

"In September 1894 I spent a few weeks in the Observatory which then existed on the summit of Ben Nevis, the highest of the Scottish hills. The wonderful optical phenomena shown when the sun shone on the clouds surrounding the hill-top, and especially the coloured rings surrounding the sun (coronas) or surrounding the shadow cast by the hill-top or observer on mist or cloud (glories), greatly excited my interest and made me wish to imitate them in the laboratory.

"At the beginning of 1895 I made some experiments for this purpose - making clouds by expansion of moist air after the manner of Coulier and Aitken. Almost immediately I came across something which promised to be of more interest than the optical phenomena which I had intended to study. Moist air which had been freed from Aitken’s dust particles, so that no cloud was formed even when a considerable degree of supersaturation was produced by expansion, did appear to give a cloud if the expansion and consequent supersaturation exceeded a certain limit..."

-C.T.R. Wilson, Nobel Prize acceptance speech, "On the cloud method of making visible ions and the tracks of ionizing particles"

First edition of the first description of WIlson's famous cloud chamber, the first type of detector to show the tracks of elementary particles.

Cloud chambers "developed from the work of Charles Wilson at the Cavendish Laboratory in the 1890's. He was interested in creating artificial mist, in order to investigate its effect on light, and did so by building a desktop-sized apparatus in which a glass chamber full of moist air was connected to a piston which could be suddenly moved outward, lowering the pressure and causing mist (or cloud) to form in the chamber. The mist droplets grow on tiny particles of dust in the air (cloud condensation nuclei). But, to his surprise, Wilson found that even when all the dust had been removed from the chamber, when the piston was rapidly moved out over a large distance a very thin mist still formed in the chamber. He surmised that the droplets were condensing around electrically charged particles (ions), and proved this, early in 1896, by operating the cloud chamber alongside a source of X-rays (X-rays had only been discovered in the preceding year) and seeing it fill up with condensation as the X-rays passing through it ionized the atoms in the air inside the chamber... Cloud chambers became an essential tool of physics (it was a cloud chamber photograph, for example, that first revealed the existence of the positron) and grew much larger, many being several meters across. They are still used, although superseded for many purposes by other detectors, including bubble chambers and wire chambers." (Gribben, Q is for Quantum). Wilson shared the 1927 Nobel Prize in Physics "for his method of making the paths of electrically charged particles visible by condensation of vapour." Also includes an early paper by Ernest Rutherford, "A Magnetic Detector of Electrical Waves and some of its Applications" (p. 1-24). A fine copy.