The quantity of force which can be brought into action in the whole of Nature is unchangeable, and can neither be increased nor diminished. - Hermann von Helmholtz

The formation of scales and of the web of harmony is a product of artistic invention, and is in no way given by the natural structure or by the natural behaviour of our hearing, as used to be generally maintained hitherto.

In speaking of the work of machines and of natural forces we must, of course, in this comparison eliminate anything in which activity of intelligence comes into play. The latter is also capable of the hard and intense work of thinking, which tries a man just as muscular exertion does.

The last decades of scientific development have led us to the recognition of a new universal law of all natural phenomena, which, from its extraordinarily extended range, and from the connection which it constitutes between natural phenomena of all kinds, even of the remotest times and the most distant places, is especially fitted to give us an idea of what I have described as the character of the natural sciences, which I have chosen as the subject of this lecture.