Thomas Young (scientist): Theory

“The theory of waves has been much simplified, and somewhat extended, and their motions have been illustrated by experiments… A similar method of reasoning has been applied to the circulation of the blood, to the propagation of sound, either in fluids or in solids, and to the vibrations of musical chords; the general principle of a velocity, corresponding to half the height of a certain modulus, being shown to be applicable to all these cases: and a connexion has been established between the sound to be obtained from a given solid, and its strength in resisting a flexure of any kind; or, in the case of ice and water, between the sound in a solid and the compressibility in a fluid state. The doctrine of sound and of sounding bodies in general has also received some new illustrations, and the theory of music and of musical intervals has been particularly discussed.”

Thomas Young (scientist)

Preface
A Course of Lectures on Natural Philosophy and the Mechanical Arts (1807)

Music , Water

“This statement appears to us to be conclusive with respect to the insufficiency of the undulatory theory, in its present state, for explaining all the phenomena of light. But we are not therefore by any means persuaded of the perfect sufficiency of the projectile system: and all the satisfaction that we have derived from an attentive consideration of the accumulated evidence, which has been brought forward, within the last ten years, on both sides of the question, is that of being convinced that much more evidence is still wanting before it can be positively decided. In the progress of scientific investigation, we must frequently travel by rugged paths, and through valleys as well as over mountains. Doubt must necessarily succeed often to apparent certainty, and must again give place to a certainty of a higher order; such is the imperfection of our faculties, that the descent from conviction to hesitation is not uncommonly as salutary, as the more agreeable elevation from uncertainty to demonstration. An example of such alternations may easily be adduced from the history of chemistry. How universally had phlogiston once expelled the aërial acid of Hooke and Mayow. How much more completely had phlogiston given way to oxygen! And how much have some of our best chemists been lately inclined to restore the same phlogiston to its lost honours! although now again they are beginning to apprehend that they have already done too much in its favour. In the mean time, the true science of chemistry, as the most positive dogmatist will not hesitate to allow, has been very rapidly advancing towards ultimate perfection.”

Thomas Young (scientist)

Miscellaneous Works: Scientific Memoirs (1855) Vol. 1 https://books.google.com/books?id=-XAXAQAAMAAJ, ed. George Peacock & John Leitch, p. 249

Way , Travel , History , Mountain

“The theory of the tides has been reduced into an extremely simple form, which appears to agree better with all the phenomena, than the more intricate calculations which they have commonly been supposed to require.”

Thomas Young (scientist)

Preface
A Course of Lectures on Natural Philosophy and the Mechanical Arts (1807)

Appearance

“In the department of physical optics, the phenomena of halos and parhelia have been explained, upon principles not entirely new, but long forgotten: the functions of the eye have been minutely examined, and the mode of its accommodation to the perception of objects at different distances ascertained: the various phenomena of coloured light have been copiously described, and accurately represented by coloured plates; and some new cases of the production of colours have been pointed out, and have been referred to the general law of double lights, by which a great variety of the experiments of former opticians have also been explained; and this law has been applied to the establishment of a theory of the nature of light, which satisfactorily removes almost every difficulty that has hitherto attended the subject.”

Thomas Young (scientist)

Preface
A Course of Lectures on Natural Philosophy and the Mechanical Arts (1807)

Law , Nature , Light

“In the astronomical and physical division of the work, will be found a general rule for determining the correction on account of aberration; a comparison of observations on the; formulae for finding the heat of summer and winter; remarks on the theory of the winds; and a comparative table of all the mechanical properties of a variety of natural bodies.”

Thomas Young (scientist)

Preface, p. x
A Course of Lectures on Natural Philosophy and the Mechanical Arts (1807)

Nature , Winter , Summer

“I met with an accident about five weeks ago in London, which has prevented my walking ever since, and I think I broke one of the metatarsal bones; this has been a favourable circumstance, for it has increased my literary application in a considerable degree. I have been studying, not the theory of the winds, but of the air, and I have made observations on harmonics which I believe are new. Several circumstances unknown to the English mathematicians which I thought I had first discovered, I since find to have been discovered and demonstrated by the foreign mathematicians; in fact, Britain is very much behind its neighbours in many branches of the mathematics: were I to apply deeply to them, I would become a disciple of the French and German school; but the field is too wide and too barren for me.”

Thomas Young (scientist)

Letter to Dr. Bostock (June, 1798) as quoted by George Peacock, Life of Thomas Young (1855)

School , Mathematics , Thinking , Study

“In the astronomical and physical division of the work, will be found a general rule for determining the correction on account of aberration; a comparison of observations on the figure of the earth; a table of the order of electrical excitation; a chart of the variation of the compass, and of the trade winds; formulae for finding the heat of summer and winter; remarks on the theory of the winds; and a comparative table of all the mechanical properties of a variety of natural bodies.”

Thomas Young (scientist)

Preface
A Course of Lectures on Natural Philosophy and the Mechanical Arts (1807)

Summer , Winter , Nature