mson supports the theory that heat was a form of motion but admits that he had been influenced only by the thought of Sir Humphry Davy and the experiments of Joule and Julius Robert von Mayer, maintaining that experimental demonstration of the conversion of heat into work was still outstanding. As soon as Joule read the paper he wrote to Thomson with his comments and questions. Thus began a fruitful, though largely epistolary, collaboration between the two men, Joule conducting experiments, Thomson analysing the results and suggesting further experiments. The collaboration lasted from 1852 to 1856, its discoveries including the Joule–Thomson effect, sometimes called the Kelvin–Joule effect, and the published results did much to bring about general acceptance of Joule's work and the kinetic theory. Thomson published more than 650 scientific papers and applied for 70 patents (not all were issued). Regarding science, Thomson wrote the following: In physical science a first essential step in the direction of learning any subject is to find principles of numerical reckoning and practicable methods for measuring some quality connected with it. I often say that when you can measure what you are speaking about and express it in numbers you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the ma