Sir—The oil you noticed yesterday turns out to be liquid chlorine.
'Yours faithfully,
'M. Faraday.' (2)
The gas had been liquefied by its own pressure. Faraday then tried compression with a syringe, and succeeded thus in liquefying the gas.
To the published account of this experiment Davy added the following note:—'In desiring Mr. Faraday to expose the hydrate of chlorine in a closed glass tube, it occurred to me that one of three things would happen: that decomposition of water would occur; … or that the chlorine would separate in a fluid state.' Davy, moreover, immediately applied the method of self-compressing atmosphere to the liquefaction of muriatic gas. Faraday continued the experiments, and succeeded in reducing a number of gases till then deemed permanent to the liquid condition. In 1844 he returned to the subject, and considerably expanded its limits. These important investigations established the fact that gases are but the vapours of liquids possessing a very low boiling-point, and gave a sure basis to our views of molecular aggregation. The account of the first investigation was read before the Royal Society on April 10, 1823, and was published, in Faraday's name, in the 'Philosophical Transactions.' The second memoir was sent to the Royal Society on December 19, 1844. I may add that while he was conducting his first experiments on the liquefaction of gases, thirteen pieces of glass were on one occasion driven by an explosion into Faraday's eye.
Some small notices and papers, including the observation that glass readily changes colour in sunlight, follow here. In 1825 and 1826 Faraday published papers in the 'Philosophical Transactions' on 'new compounds of carbon and hydrogen,' and on 'sulphonaphthalic acid.' In the former of these papers he announced the discovery of Benzol, which, in the hands of modern chemists, has become the foundation of our splendid aniline dyes. But he swerved incessantly from chemistry into physics; and in 1826 we find him engaged in investigating the limits of vaporization, and showing, by exceedingly strong and apparently conclusive arguments, that even in the case of mercury such a limit exists; much more he conceived it to be certain that our atmosphere does not contain the vapour of the fixed constituents of the earth's crust. This question, I may say, is likely to remain an open one. Dr. Rankine, for example, has lately drawn attention to the odour of certain metals; whence comes this odour, if it be not from the vapour of the metal?
In 1825 Faraday became a member of a committee, to which Sir John Herschel and Mr. Dollond also belonged, appointed by the Royal Society to examine, and if possible improve, the manufacture of glass for optical purposes. Their experiments continued till 1829, when the account of them constituted the subject of a 'Bakerian Lecture.' This lectureship, founded in 1774 by Henry Baker, Esq., of the Strand, London, provides that every year a lecture shall be given before the Royal Society, the sum of four pounds being paid to the lecturer. The Bakerian Lecture, however, has long since passed from the region of pay to that of honour, papers of mark only being chosen for it by the council of the Society. Faraday's first Bakerian Lecture, 'On the Manufacture of Glass for Optical Purposes,' was delivered at the close of 1829. It is a most elaborate and conscientious description of processes, precautions, and results: the details were so exact and so minute, and the paper consequently so long, that three successive sittings of the Royal Society were taken up by the delivery of the lecture. (3) This glass did not turn out to be of important practical use, but it happened afterwards to be the foundation of two of Faraday's greatest discoveries. (4)
The experiments here referred to were commenced at the Falcon Glass Works, on the premises of Messrs. Green and Pellatt, but Faraday could not conveniently attend to them there. In 1827, therefore, a furnace was erected in the yard of the Royal Institution; and it was at this time, and with a view of assisting him at the furnace, that Faraday engaged Sergeant Anderson, of the Royal Artillery, the respectable, truthful, and altogether trustworthy man whose appearance here is so fresh in our memories. Anderson continued to be the reverential helper of Faraday and the faithful servant of this Institution for nearly forty years. (5)
In 1831 Faraday published a paper, 'On a peculiar class of Optical Deceptions,' to which I believe the beautiful optical toy called the Chromatrope owes its origin. In the same year he published a paper on Vibrating Surfaces, in which he solved an acoustical problem which, though of extreme simplicity when solved, appears to have baffled many eminent men. The problem was to account for the fact that light bodies, such as the seed of lycopodium, collected at the vibrating parts of sounding plates, while sand ran to the nodal lines. Faraday showed that the light bodies were entangled in the little whirlwinds formed in the air over the places of vibration, and through which the heavier sand was readily projected. Faraday's resources as an experimentalist were so wonderful, and his delight in experiment was so great, that he sometimes almost ran into excess in this direction. I have heard him say that this paper on vibrating surfaces was too heavily laden with experiments.
Footnotes to Chapter 2
(1) The reader's attention is directed to the concluding
paragraph of the 'Preface to the Second Edition written in
December, 1869. Also to the Life of Faraday by Dr. Bence
Jones, vol. i. p. 338 et seq.
(2) Paris: Life of Davy, p. 391.
(3) Viz., November 19, December 3 and 10.
(4) I make the following extract from a letter from Sir John
Herschel, written to me from Collingwood, on the 3rd of
November, 1867:—'I will take this opportunity to mention
that I believe myself to have originated the suggestion of
the employment of borate of lead for optical purposes. It
was somewhere in the year 1822, as well as I can recollect,
that I mentioned it to Sir James (then Mr.) South; and, in
consequence, the trial was made in his laboratory in
Blackman Street, by precipitating and working a large
quantity of borate of lead, and fusing it under a muffle in
a porcelain evaporating dish. A very limpid (though
slightly yellow) glass resulted, the refractive index 1.866!
(which you will find set down in my table of refractive
indices in my article "Light," Encyclopaedia Metropolitana).
It was, however, too soft for optical use as an object-
glass. This Faraday overcame, at least to a considerable
degree, by the introduction of silica.'
(5) Regarding Anderson, Faraday writes thus in 1845:—'I
cannot resist the occasion that is thus offered to me of
mentioning the name of Mr. Anderson, who came to me as an
assistant in the glass experiments, and has remained ever
since in the laboratory of the Royal Institution. He
assisted me in all the researches into which I have entered
since that time; and to his care, steadiness, exactitude,
and faithfulness in the performance of all that has been
committed to his charge, I am much indebted.—M. F.' (Exp.
Researches, vol. iii. p. 3, footnote.)
Chapter 3.
Discovery of Magneto-electricity: Explanation of Argo's
magnetism of rotation: Terrestrial magneto-electric