Thomson used Newton's Second Law to obtain a general formula... to interpret measurements of the cathode-ray deflection... produced by... electric or magnetic forces... In his cathode ray tube, the ray particles pass through... the deflection region... subjected to electric and magnetic forces... at right angles to their original direction... then through a much longer force-free... drift region... in which they drift freely until they hit the end of the tube... [a] glowing spot... The forces exerted on the cathode ray particles give them an acceleration at right angles to the axis of the tube, so... the particles have a small component of velocity at right angles to their original motion... equal to the product of the acceleration and the time... in the [very short] deflection region... [T]he downward displacement of the ray when it hits the end of the tube is the downward velocity produced in the deflection region times the length of time... in the drift region... [T]he electric force... on a particle is proportional to the [particle's] electric charge... [U]nlike the electric force, the magnetic force... on a particle is proportional to the particle's velocity as well as its charge. By measuring... deflections due to... [both] forces, Thomson... could determine both the ray-particle velocities and the ratio of their charge and mass.

[I]n 1897 Thomson... detected a deflection... by electric forces between the rays and the electrified metal plates. ...due largely to the use of better vacuum pumps ...to where the effects of residual gas ...became negligible. (Some evidence for... deflection was [also] found... by Goldstein.) [D]eflection was toward the positively charged plate... away from the negatively charged one, confirming Perrin... that the rays carry negative electric charge.

Hertz showed... the... rays were not appreciably deflected by electrified metal plates. This seemed to rule out... electrically charged particles... Hertz concluded the rays were some sort of wave... the nature of light was... not well understood, and a magnetic deflection did not seem impossible. In 1891 Hertz made a further observation... to support the wave theory... The rays could penetrate thin foils of gold and other metals, much as light penetrates glass. ...We know now that... the... particles were traveling so fast, and the electric forces were so weak... the deflection was too small to observe.

Having discovered the existence of a new kind of rays, I of course began to investigate what they would do. … It soon appeared from tests that the rays had penetrative power to a degree hitherto unknown. They penetrated paper, wood, and cloth with ease; and the thickness of the substance made no perceptible difference, within reasonable limits. … The rays passed through all the metals tested, with a facility varying, roughly speaking, with the density of the metal. These phenomena I have discussed carefully in my report to the Würzburg society, and you will find all the technical results therein stated.

Coulomb used a... device of his own invention, the torsion balance, to measure forces between small pith balls. The inverse-square law was found to hold accurately...

It was in the year 1843 that I read a paper "On the Calorific Effects of Magneto-Electricity and the Mechanical Value of Heat" to the Chemical Section of the British Association assembled at Cork. With the exception of some eminent men, among whom I recollect with pride Dr. Apjohn, the president of the Section, the Earl of Rosse, Mr. Eaton Hodgkinson, and others, the subject did not excite much general attention; so that when I brought it forward again at the meeting in 1847, the chairman suggested that, as the business of the section pressed, I should not read my paper, but confine myself to a short verbal description of my experiments. This I endeavoured to do, and discussion not being invited, the communication would have passed without comment if a young man had not risen in the section, and by his intelligent observations created a lively interest in the new theory. The young man was William Thomson, who had two years previously passed the University of Cambridge with the highest honour, and is now probably the foremost scientific authority of the age.

Perrin... showed in 1895 that the rays deposit negative electrical charge on a charge collector... inside... the tube.

Plücker's student J. W. Hittorf... observed that solid bodies... near a small cathode would cast shadows... [and] deduced... the rays travel... in straight lines.

...by action on man all known force may be measured. Indeed, few men of science measured force in any other way. After once admitting that a straight line was the shortest distance between two points, no serious mathematician cared to deny anything that suited his convenience, and rejected no symbol, proved or unproveable, that helped him to accomplish work. The symbol was force, as a compass-needle or a triangle was force.

Long before the discovery of radium led to the recognition of the electron as the common constituent of all the bodies previously described as chemical elements, the minute particles of matter in question had been identified with the cathode rays observed in Sir William Crookes' vacuum tubes. When an electric current is passed through a tube from which the air (or other gas it may contain) has been almost entirely exhausted, a luminous glow pervades the tube manifestly emanating from the cathode or negative pole of the circuit. This effect was studied by Sir William Crookes very profoundly. Among other characteristics it was found that, if a minute windmill was set up in the tube before it was exhausted, the cathode ray caused the vanes to revolve, thus suggesting the idea that they consisted of actual particles driven against the vanes; the ray being thus evidently something more than a mere luminous effect. Here was a mechanical energy to be explained, and at the first glance it seemed difficult to reconcile the facts observed with the idea creeping into favour, that the particles, already invested with the name "electron," were atoms of electricity pure and simple. Electricity was found, or certain eminent physicists thought they had found, that electricity per se had inertia. So the windmills in the Crookes' vacuum tubes were supposed to be moved by the impact of electric atoms.

Long before the discovery of radium led to the recognition of the electron as the common constituent of all the bodies previously described as chemical elements, the minute particles of matter in question had been identified with the cathode rays observed in Sir William Crookes' vacuum tubes. When an electric current is passed through a tube from which the air (or other gas it may contain) has been almost entirely exhausted, a luminous glow pervades the tube manifestly emanating from the cathode or negative pole of the circuit. This effect was studied by Sir William Crookes very profoundly. Among other characteristics it was found that, if a minute windmill was set up in the tube before it was exhausted, the cathode ray caused the vanes to revolve, thus suggesting the idea that they consisted of actual particles driven against the vanes; the ray being thus evidently something more than a mere luminous effect. Here was a mechanical energy to be explained, and at the first glance it seemed difficult to reconcile the facts observed with the idea creeping into favour, that the particles, already invested with the name "electron," were atoms of electricity pure and simple. Electricity was found, or certain eminent physicists thought they had found, that electricity per se had inertia. So the windmills in the Crookes' vacuum tubes were supposed to be moved by the impact of electric atoms.

In order to receive in the eye all the light diffracted through a narrow opening, and to see the phenomena strongly magnified; still more in order to directly measure the inflection of the light, I placed in front of the objective of a theodolite-telescope a screen in which there was a narrow vertical opening which could be made wider or narrower by means of a screw. By means of a heliostat I threw sunlight into a darkened room through a narrow slit so that it fell upon this screen, through whose opening the light was therefore diffracted. I could then observe through the telescope the phenomena produced by the diffraction, magnified, and yet seen with sufficient brightness; and at the same time I could measure the angles of inflection of the light by means of the theodolite.

He had been trying to measure the distance between the earth and God.

As the cathode rays carry a charge of negative electricity, are deflected by an electrostatic force as if they were negatively electrified, and are acted on by a magnetic force in just the way in which this force would act on a negatively electrified body moving along the path of these rays, I can see no escape from the conclusion that they are charges of negative electricity carried by particles of matter.