The finest imagination in the world could not have conceived of a better idea than the philosophers' stone to inspire the minds and faculties of men. Without it, chemistry would not be what it is today. In order to discover that no such thing as the philosopher's stone existed, it was necessary to ransack and analyze every substance known on earth. And in precisely this lay its miraculous influence.

What struck me most in England was the perception that only those works which have a practical tendency awake attention and command respect, while the purely scientific, which possess far greater merit are almost unknown. And yet the latter are the proper source from which the others flow. Practice alone can never lead to the discovery of a truth or a principle. In Germany it is quite the contrary. Here in the eyes of scientific men no value, or at least but a trifling one, is placed upon the practical results. The enrichment of science is alone considered worthy attention.

There are various causes for the generation of force: a tensed spring, an air current, a falling mass of water, fire burning under a boiler, a metal that dissolves in an acid-one and the same effect can be produced by means of all these various causes. But in the animal body we recognise only one cause as the ultimate cause of all generation of force, and that is the reciprocal interaction exerted on one another by the constituents of the food and the oxygen of the air. The only known and ultimate cause of the vital activity in the animal as well as in the plant is a chemical process.

In the progressive growth of astronomy, physics or mechanical science was developed, and when this had been, to a certain degree, successfully cultivated, it gave birth to the science of chemistry.

We may fairly judge of the commercial prosperity of a country from the amount of sulphuric acid it consumes.

I have learnt that all our theories are not Truth itself, but resting places or stages on the way to the conquest of Truth, and that we must be contented to have obtained for the strivers after Truth such a resting place which, if it is on a mountain, permits us to view the provinces already won and those still to be conquered.

Only about seventy years ago was chemistry, like a grain of seed from a ripe fruit, separated from the other physical sciences. With Black, Cavendish and Priestley, its new era began. Medicine, pharmacy, and the useful arts, had prepared the soil upon which this seed was to germinate and to flourish.