It is necessary to guard against a possible danger... of submitting too readily to the result of a so-called "crucial experiment". Very few experimen… - J. R. Partington

The statement of a law of nature involves the formation of a concept, or general idea, in which the likenesses of phenomena are collected, and the differences, in so far as they are not intimately involved in the nature of the case, are eliminated.

On the one hand, the student has been informed by some writers that the only certain way lies in the use of the entropy-function and the thermodynamic potentials; on the other hand, he is told with equal authority that the method used by the original investigators has been the consideration of cyclic processes, and that the former method is nothing but a mathematical (perhaps unnecessary) refinement of the results obtained by the latter. These extreme attitudes appear to me to be unfortunate, and more especially when one observes the physical clearness introduced by the use of cyclic processes, but at the same time remembers that most of the results obtained by separate investigators using cyclic processes had, with a great many more, previously been found by J. Willard Gibbs by means of a purely analytical method.

The blue dye indigo was obtained from the indigo plant by the Egyptians more than 4000 years ago. ...The famous and valuable "purple of Tyre" was perhaps first made in Crete in very early times... obtained at great cost... from tiny marine molluscs. ...The scarlet dye mentioned in the Bible was obtained from the kermes insect (hence the name "crimson").