What I find amazing about James Thomson is that he was no shoe salesman, yet he was totally overshadowed by his older brother William...a guy you might have heard of by the name of Lord Kelvin.
Lord Kelvin's less famous brother Jimmy was the president of the Scottish Society of Shipbuilders and Engineers from 1884-1886. He was a true scientific Renaissance man, who did research into glacier motion and the flow of rivers, and who also invented a type of accelerated turbine used for underwater vehicles. He was also the first person to invent the term "interface," a word to this day. He was the closest thing in reality to one of those TV scientists like Dr. Benton Quest that can do Nuclear Physics one day and anthropology and linguistics the next.
James Thomson's best contributions by far were to the field of mathematics. Based on the work of the Bavarian engineer J.H. Hermann, Jimmy created an improved version of the polar planimeter - an instrument that allows area to be determined on a flat surface of any arbitrary and irregular shape.
What's more, he was the first to coin the term "radian" for the single most useful angle of measurement in calculus, the length of an arc of a sliced of subtended angle that is equal to the radius of a circle. Radians are useful because they allow derivative and integral identities to be expressed in very short time-saving terms. What's more, in trigonometry, the relationship between sine and cosine angles can only really be expressed in radians and it's extremely awkward to represent in any other way.
Among other things, radians are useful in determining the speed of rotation (something physicists call angular velocity). The radian is also used in (God help us) Quantum Mechanics, where it is necessary to describe the functions of Planck's Constant. According to Max Planck, the flow of energy is determined by fundamental "bits" in the universe, Quantum. Energy can't assume any given variable range, but only on a finite set of ranges determined by grouping Quanta. It's possible to make something move a "little bit faster" or making something "a little bit brighter" because the amount of Quanta involved are very, very tiny so they're invisible to the everyday scale. Planck's Constant is used to describe the scale of quanta as the smallest amount of energy a quanta can have, and it is necessary to use radians to understand it because when applying Planck's constant to energy, you need to figure out the relationship between quanta and frequency, which comes in waves as in trigonometry.
This was the guy that was Lord Kelvin's "less famous" brother! Amazing! Why would a guy like this be known as the lesser of the two brothers, anyway?
Because Lord Kelvin did nothing short of create the unifying principles of physics, almost like Darwin created the unifying principles of the biological sciences. He codified the Laws of Thermodynamics, and connected how heat functioned in a way similar to that of electric charges, a unifying idea that was one of the most crucial in the history of science. Though Faraday discovered that electromagnetism needs a medium to flow, it was Lord Kelvin that put forth the mathematical models for how that could be. It was also Lord Kelvin who speculated on the idea of a possible "absolute zero," and the idea that heat is actually a form of motion.
All that said, why is it that Lord Kelvin is better remembered than his engineer brother? Scientists are often called impractical Ivory Tower people, especially in the face of "doers" like engineers and industrial scientists. Scientists that work with "theory" (a term misunderstood by people outside of science) are viewed as less crucial to the world than inventors and practical people. Alas, in the end, it is the theorists that end up being ultimately more important because theories in science are not half-baked guesses, but grand, unifying ideas that explain facts and make predictions. More is ultimately learned, and more ultimately comes out of a theory. Lord Kelvin tried his hand at being an engineer, too, like his famous brother, but more people remember his formulation of the laws of thermodynamics than his efforts at telegraphing and his building a newer and better galvanometer.