John Tyndall

The Bakerian lecture—On the absorption and radiation of heat by gases and vapours, and on the physical connexion of radiation, absorption, and conduction

The apparatus made use of in this investigation consists of the following parts :— 1. A copper cube C, containing water kept constantly boiling, and one of whose faces, coated with lampblack, forms the source of radiant heat. 2. A brass tube 2·4 inches in diameter, which is divided into two portions, α and β.

On the Optical Deportment of the Atmosphere in Reference to the Phenomena of Putrefaction and Infection

The author refers in an Introduction to an inquiry on the decomposition of vapours and the formation of active clouds by light, whereby he was led to experiment on the floating matter of the air. He refers to the experiments of Schwann, Schroder, and Dusch, Schroder himself, to those of the illustrious Prench chemist Pasteur, to the reasoning of Lister and its experimental verification regarding the filtering-power of the lungs; from all of which he concluded, six years ago, that the power of developing life by the air, and its power of scattering light, would be found to go hand in hand. He thought the simple expedient of examining by means of a beam of light, while the eye was kept sensitive by darkness, the character of the medium in which their experiments were conducted could not fail to be useful to workers in this field. But the method has not been much turned to account; and this year he thought it worth while to devote some time to the more complete demonstration of its utility. He also wished to free his mind, and if possible the minds of others, from the uncertainty and confusion which now beset the doctrine of “spontaneous generation.” Pasteur has pronounced it “a chimera,” and expressed the undoubting conviction that this being so it is possible to remove parasitic diseases from the earth. To the medical profession, therefore, and through them to humanity at large, this question is one of the last importance. But the state of medical opinion regarding it is not satisfactory. In a recent Humber of the ‘ British Medical Journal/ and in answer to the question, “ In what way is contagium generated and communicated” Messrs. Braidwood and Yacher reply that, notwithstanding “an almost incalculable amount of patient labour, the actual results obtained, especially as regards the manner of generation of contagium, have been most disappointing. Observers are even yet at variance whether these minute particles, whose discovery we have just noticed, and other disease-germs, are always produced from like bodies previously existing, or whether they do not, under certain favourable conditions, spring into existence de novo”.

On the Action of Rays of High Refrangibility upon Gaseous Matter

Within the last ten years I have had the honour of submitting to the Royal Society a series of investigations the principal aim of which was to render the less refrangible rays of the spectrum interpreters and expositors of the molecular condition of matter. Unlike the beautiful researches of Melloni and Knoblauch, these inquiries made radiant heat a means to an end. My thoughts were fixed on it in relation to the matter through which it passed. Placing before my mind such images of molecules and their constituents as modem science justifies or renders probable, such images of the luminiferous ether and its motions as the undulatory theory enables us to form, I endeavoured to fashion and execute experiments founded upon these conceptions which should give us a surer hold upon molecular constitution.

On the Atmosphere as a Vehicle of Sound

The cloud produced by the puff of a locomotive can quench the rays of the noonday sun; it is not therefore surprising that in dense fogs our most powerful coast-lights, including even the electric light, should become useless to the mariner. Disastrous shipwrecks are the consequence. During the last ten years no less than two hundred and seventy-three vessels have been reported as totally lost on our own coasts in fog or thick weather. The loss, I believe, has been far greater on the American seaboard, where trade is more eager and fogs more frequent than they are here. No wonder, then, that earnest efforts should have been made to find a substitute for light in sound-signals, powerful enough to give warning and guidance to mariners while still at a safe distance from the shore.

On Some Physical Properties of Ice

The observations upon Glaciers, to be recorded in a subsequent paper, led me to make some experiments upon the physical properties of ice, the results of which are, I hope, of sufficient interest to justify me in presenting them to the Royal Society.

On the Structure and Motion of Glaciers

In a lecture given at the Royal Institution on the 6th of June, by Mr. Tyndall, 1856, certain views regarding the origin of slaty cleavage were brought forward, and afterwards reported in the ‘Proceedings’ of the Institution. A short time subsequently, the attention of the lecturer was drawn by Mr. Huxley to the observations of Professor J. D. Forbes on the veined or laminar structure of glacier ice, and the surmise was expressed, that the same explanation might apply to it as to slaty cleavage. On consulting the observations referred to, the probability of the surmise seemed apparent, and the result was a mutual arrangement to visit some of the Swiss glaciers, for the purpose of observing the structure of the ice. This arrangement was carried out, the field of observation comprising the glaciers of Grindelwald, the Aar, and the Rhone. After returning to England, the one in whose department it more immediately lay, followed up the inquiry, which gradually expanded, until at length it touched the main divisions of the problem of glacier structure and motion. An account of the experiments and observations, and our joint reflections on them, are embodied in the memoir now submitted to the Royal Society.

V. Note on the influence exercised by light on organic infusions

Early last June I took with me to the Alps 50 small hermetically sealed flasks containing infusion of cucumber, and 50 containing nip infusion. Before sealing they had been boiled for five minutes the laboratory of the Royal Institution. They were carefully cked in sawdust, but when unpacked the fragile sealed ends of out 20 of them were found broken off. Some of these injured tsks were empty, while others still retained their liquids. The 80 broken flasks were found pellucid, and they continued so throughout summer. All the broken ones, on the other hand, which had tained their liquids, were turbid with organisms.

On the Absorption and Radiation of Heat by Gaseous Matter. Second Memoir

Resuming with a new apparatus his experiments on the influence of chemical combination on the absorption and radiation of heat by gases, the author in the present investigation first examines the deportment of chlorine as compared with hydrochloric acid, and of bromine as compared with hydrobromic acid, and finds that the act of combination, which in each of these two cases notably diminishes the density of the gas, and renders the coloured gas perfectly transparent to light, renders it more opake for obscure heat. He also draws attention to the fact that sulphur, which is partially opake to light, is transparent to 54 per cent, of the rays issuing from a source of 100°C., while its compound, heavy spar, which is sensibly transparent to light, is quite opake to the rays from a source of 100°C.

Observations on Glaciers.

On the 6th of June, 1856, certain views were advanced by one of us on the origin of slaty cleavage, and soon afterwards his attention was drawn by the other to the observations of Prof. J. D. Forbes on the structure of glacier ice, as suggesting the idea that the ice structure might be due to the same cause as the slate cleavage. On consulting the observations referred to, the lecturer at once perceived the probability of the surmise, and the consequence was a joint visit for a few days to the glaciers of Grindelwald, the Rhone, and the Aar. The subject being a physical one, it was followed up by the physicist on his return from the Continent.

On the Absorption and Radiation of Heat by Gaseous and Liquid Matter. Fourth Memoir

In his former researches on the absorption and radiation of heat by gaseous matter, the author compared different gases and vapours at a common thickness with each other. In the first part of the present communication he determines, in the case of several gases and vapours, the absorption effected by different thicknesses of the same gaseous body. His least thickness was 0·01 of an inch, and his greatest 49·4 inches; thus the thickness varied from 1 to nearly 5000.