Lives of the electricians

by William T. Jeans

In a subsequent memoir he dealt with the influence of colour and mechanical condition upon radiant heat, demonstrating that white bodies are far more potent absorbers of radiant heat than black ones.

During the first thirteen years of his researches in the laboratory of the Royal Institution he produced thirteen papers, which were published in the Philosophical Transactions. Conspicuous among these were his papers on the radiation and absorption of heat, and his researches on that subject have generally been admitted to be of the most thorough and original character. A lucid epitome of the chief results he obtained was given in the Rede lecture which he delivered before the University of Cambridge in 1865, when the University conferred on him the honorary degree of LL.D.

In 1863 he published the first edition of one of his most popular books, Heat Considered as a Mode of Motion—a book which an eminent electrician has recommended students of electricity to master; in 1867 he published a volume of lectures on “Sound”; and in 1869-74 he published his lectures on “Light.” These works have gone through several editions. As an illustration of the interest with which he can invest such impalpable subjects, it is worth remarking that a Chinese official, named Hsii-chung-hu, was so pleased with the book on Sound that he had it translated into the Chinese language and printed at Shanghai, in order that his countrymen might participate in the pleasure and instruction which he had derived from it. It was published at the expense of the Chinese Government, and sold at 1s. 6d. a copy.

During the ten years from 1859 to 1869, says Professor Tyndall, “researches on radiant heat in its relations to the gaseous form of matter occupied my continual attention.” But towards the close of that period his main inquiry, as it extended into space, began to spread out into various branches. In 1866 he entered upon an examination of the chemical action of light upon vapours, and the action of heat of high refrangibility as an explorer of the molecular condition of matter. “In this investigation one obstacle to be overcome was the presence of the floating matter in the air. The processes for the removal of these particles became the occasion of an independent research, branching out into various channels: on the one hand, it dealt with the practical problem of the preservation of life among firemen exposed to heated smoke; and, on the other, it approached the recondite question of spontaneous generation. He subjected the compound vapours of various substances to the action of a concentrated beam of light. The vapours were decomposed, and non-volatile products were formed. The decompositions always began with a blue cloud, which discharged perfectly polarised light at right angles to the beam. This suggested to him the origin of the blue colour of the sky; and as it showed the extraordinary amount of light that may be scattered by cloudy matter of extreme tenuity, he considered that it might be regarded as a suggestion towards explaining the nature of a comet’s tail.”

Regions of cloud and smoke are proverbial as symbols of the negation of human interest; but Professor Tyndall imparted new beauties to the one and deprived the other of its terrors. He said to the chaotic vapours “Light,” and that which was without form and void instantly assumed the loveliest forms that Nature knows. Incredible as this language may appear to some, it is no mere Oriental hyperbole. He made the light from an electric lamp to pass through a great glass tube containing transparent, invisible vapours, and the action of the light at once commencing chemical decomposition, various cloud forms resembling organic structures were seen in the tube. The following is the beautiful description he gave to the Royal Society of the phenomena presented by hydriodic acid:—

“The cloud extended for about eighteen inches along the tube, and gradually shifted its position from the end nearest the lamp to the most distant end. The portion quitted by the cloud proper was filled by an amorphous haze, the decomposition, which was progressing lower down, being here apparently complete. A spectral cone turned its apex towards the distant end of the tube, and from its circular base filmy drapery seemed to fall. Placed on the base of the cone was an exquisite vase, from the interior of which sprang another vase of similar shape; over the edges of these vases fell the faintest clouds, resembling spectral sheets of liquid. From the centre of the upper vase a straight cord of cloud passed for some distance along the axis of the experimental tube, and at each end of this cord two involved and highly iridescent vortices were generated. The frontal portion of the cloud which the cord penetrated assumed in succession the form of roses, tulips, and sunflowers. It also passed through the appearance of a series of beautifully-shaped bottles placed one within the other. Once it presented the shape of a fish, with eyes, gills, and feelers.”

In 1869 it was stated before the British Association that M. Morren, while living in the South of France, had succeeded in producing similar results by the use of sunlight instead of the electric light.

For a long time during his researches on the decomposition of vapours he was troubled by the presence of floating matter revealed by a powerful condensed beam of light, and he tried numerous expedients for the purpose of intercepting this matter. At last he succeeded. By causing the air intended for experimental purposes to pass over the tip of a spirit-lamp flame, the floating matter disappeared. He therefore concluded that it was organic matter, which had been burned out by the flame. This discovery took place on October 5th, 1868. Till then he regarded the dust of our air as for the most part inorganic and noncombustible. This led him on to the investigation of the germ theory. On the one hand he added proof to proof, and experiment to experiment, to show that when a consuming heat was applied to air its organic matter disappeared; and on the other hand he maintained that as surely as a fig comes from a fig, a grape from a grape, and a thorn from a thorn, so surely does the typhoid virus or seed, when planted or scattered about among people, increase and multiply into typhoid fever, scarlatina virus into scarlatina, and small-pox virus into small-pox. These conclusions formed the subject of a famous lecture on “Dust and Disease,” delivered at the Royal Institution on January 21st, 1870. Among his audience were some of the foremost men of the day, such as Mr. W. E. Gladstone, then Prime Minister, Earl Granville, Dean Stanley, Sir Edwin Landseer, Sir Henry Holland, and Professor Huxley. The views which Professor Tyndall then put forth were received with marked disfavour among the medical profession. Even scientific men did not hesitate to pour ridicule upon the germ theory. For example, Professor Bloxam, Lecturer on Chemistry to the Department of Artillery Studies, suggested in one of his lectures that the Committee on Explosives should abandon gun cotton, and collecting the germs of small-pox and similar malignant diseases in cotton or other dust-collecting substances, should load shells with them, and we should then hear of the enemy being dislodged from his position by a volley of typhus or a few rounds of Asiatic cholera. Like most truths, the germ theory survived the ridicule of its opponents.

The labours of Pasteur in relation to the germ theory always appeared to command Professor Tyndall’s admiration. A large part of his lecture on “Dust and Disease” consisted of an account of the successful way in which Pasteur dealt with the epidemic among silkworms in France. Writing in April, 1870, the Professor said: “There is more solid science in one paper of Pasteur than in all the volumes and essays that have been written against him. Schroeder and Pasteur have demonstrated that air filtered through cotton-wool is deprived wholly, or in part, of its power to produce animalcular life. Why? An experiment with a beam of light answers the question; for while it proves our ordinary air to be charged with floating matter, the beam pronounces air, which has been carefully filtered through cotton-wool, to be visibly pure; there are no germs afloat in it; hence it is impossible as a generator of life. Again, Pasteur prepared twenty-one flasks, each containing a decoction of yeast, which he boiled in order to destroy whatever germs it might contain. While the space above the liquid was filled with pure steam he sealed the necks of his flasks with a blow-pipe. He opened ten of them in the damp, still caves of the Paris Observatory, and eleven of them in the courtyard of the same establishment. Of the former only one showed signs of life subsequently. In nine out of the ten flasks no organisms of any kind were developed. In all the others organisms speedily appeared. Pasteur ascribed this unexpected result to the subsidence of the germs in the motionless air of the caves. Is this surmise correct? The beam of light enables us to answer this question. I have had a chamber constructed, the lower half of which is of wood, and the upper half of glass. On the 6th February this chamber was closed, and every crevice that could admit dust or cause a disturbance of the air was carefully stopped. The electric beam when sent through the glass showed the air at the outside to be loaded with floating matter. The chamber was examined almost daily, and a gradual diminution of the floating matter was observed. At the end of the week the chamber was optically empty. The floating matters, germs included, had wholly subsided, and the air held nothing in suspension. Here again the ocular demonstration furnished by the luminous beam goes hand in hand with the experimental result of Pasteur.”

Professor Tyndall did not, however, adopt the germ theory on the authority of Pasteur. He not only discovered it for himself, but demonstrated its accuracy by innumerable experiments, in the course of which he made use of 10,000 vessels. To him, too, science owes the use of the electric beam as an explorer of germ particles which could not otherwise be made visible by the best optical aids. The most exquisitely minute particles, which could not be detected by the most powerful glasses, have been revealed in the air by the electric beam.