Lives of the electricians

by William T. Jeans

Professor Tyndall also exhibited, both at the Royal Institution and at the Royal Society, Faraday’s marvellous experiment showing the magnetisation of light, which he described as Faraday’s third great discovery, and compared “to the Weisshorn among mountains—high, beautiful, and alone.” In a dark room a ray of light from a lamp passed between the poles of a large horse-shoe, and appeared as a spot of light on a screen. When by connecting a battery with the horse-shoe, the latter became powerfully magnetic, the spot of light was instantly moved on the screen, being visibly deflected by the magnetism of the horse-shoe.

To illustrate the velocity of the electric current he showed that a spark sent through a copper wire which passed through some gunpowder, did not ignite the gunpowder, because it had not time; but when a wet string—a slower conductor—was substituted for the copper wire, the passage of the current was retarded and the powder ignited. Another illustration of an accidental character he frequently narrated. While lecturing to an audience of young and old people at the Royal Institution, he caused fifteen Leyden jars to be charged with electricity, and by some awkwardness his shoulder touched the conductor leading from the jars. “I am extremely sensitive to electricity,” he said, “yet a charge from such a powerful battery as fifteen jars seemed to have no disastrous effect upon me. I stood perfectly still, wondering that I did not feel it; but I knew something had occurred; and after standing for a moment or two I seemed to open my eyes, which probably were open all the time. I saw a confused mass of apparatus about me. I felt it necessary to reassure the people before me, so I said: ‘Over and over again I have wanted that battery to be discharged into me, and now I have had it.’ Although I appeared unaffected, really the optic nerve in me was so affected that I saw my arm severed from my body. I soon, however, recovered proper sight, and saw that I was all right.” The explanation given for his intellect being thus clear while his vision was distorted, is that the electric current moved with much greater rapidity than the nervous agency by which the consciousness of pain is excited. According to Professor Bois-Reymond, the latter moves at the rate of ninety-eight feet per second, while, according to Professor Wheatstone, electricity moves in a copper wire at the rate of 288,000 miles per second. Hence it is probable that death by electricity or lightning is painless.

In a course of lectures delivered to a juvenile audience in December, 1884, he gave a fresh illustration of the ease with which electricity can be generated in a rather unusual way. It is stated in text-books on electricity that if a man could be suspended between the poles of a common magnet, he would point equatorially, because all the substances of which he is made are diamagnetic. Professor Tyndall, however, showed how easily his body could be made to act the part of a magnet. In the presence of his audience, a man repeatedly struck the back of the Professor’s coat with a piece of catskin, and in a minute or two sufficient electricity was generated to make his hand, held out in front of him, magnetic and capable of attracting to it different objects, just as a small magnet attracts bits of iron near it. He stated that this experiment had never, so far as he knew, been performed before.

In other lectures he illustrated the resistance of a telegraph cable to the transmission of the electric current over a length of 14,000 miles, by introducing into the path of the current gaps containing feebly conducting liquids, so distributed as to represent intervals equal to those in telegraphing between Gibraltar, Malta, Suez, Aden, Bombay, Calcutta, Rangoon, Singapore, Java, and Australia. Connected with these gaps were mirrors which cast ten dots of light on a large screen, being one for each gap or station; when the electric current was sent through the miniature cable, it so deflected a needle attached to each mirror as to cause dot after dot to start aside upon the screen. The interval between the movement of each dot of light exactly represented the time which the electric current would require to reach the several stations named in the working of a real cable. He thus strikingly illustrated the fact that the resistance of a cable depends in some degree upon its length, and visibly showed the time consumed in overcoming that resistance. To show the different resistances of different metals and how resistance produces heat, he took pieces of platinum and silver, and arranging them alternately in a long line, sent an electric current through them. Thereupon each piece of platinum, being a metal of great resisting power, glowed with a brilliant red heat, while the intervening pieces of silver, being good conductors, were invisible.

In 1878 he was exhibiting and explaining to a Parliamentary Committee the electrical effects produced in working by hand a dynamo machine, when Lord Lindsay asked, as “an elementary question,” what was the source of the mechanical power by which he was able to turn the wheel of the dynamo. The Professor explained that it was simply the combustion of the fat and tissues of his muscle. “Then will you explain,” said Lord Lindsay, “how it is that as the temperature of your muscle and your blood is only 100°, you get it up to fuse a wire which would require a temperature of 3,500°.” To that the Professor replied: “I would give all that I possess to be able fully to answer that question; but this much is absolutely certain, that all the heat developed in that dynamo, amounting to between 3,000° and 4,000° Fahr., is certainly derived from the combustion of my muscle. It is nothing more mysterious than the combustion of zinc in the voltaic battery.”

The facility with which he extemporises illustrations to make science entertaining appears from the following incident. “On one occasion,” he says, “I paid a visit to a large school in the country, and was asked by the principal to give a lesson to one of the classes. I agreed to do so provided he would let me have the youngest boys in his school. To this he willingly assented; and after casting about in my mind as to what could be said to the little fellows, I went to a village hard by and bought a quantity of sugar-candy. This was my only teaching apparatus. When the time for assembling the class had arrived I began by describing the way in which sugar-candy and other artificial crystals were formed, and tried to place vividly before their young minds the architectural process by which the crystals were built up. They listened to me with the most eager interest. I examined the crystal before them, and when they found that in a certain direction it could be split into thin laminæ with shining surfaces of cleavage, their joy was at its height. They had no notion that the thing they had been crunching and sucking all their lives embraced so many hidden points of beauty.” That incident occurred many years ago; and as illustrating his own perennial admiration of the phenomena of crystallisation another incident may be added that occurred in a lecture delivered in the Royal Institution in 1855. He was exhibiting the effect of applying an electric current by means of two wires to acetate of lead—vinegar and lead. The mixture becoming decomposed, the atoms of water appeared, when magnified and reflected on a large screen, as beautiful rings moving up and down the one wire, while the atoms of lead on the other wire formed themselves by crystalline action into pretty fern-like leaves and plants of all shapes and sizes. “Is not that beautiful?” said the Professor; “I have seen it done a hundred times, but I can never see it without wonder.”

Professor Tyndall has seen the triumph of several scientific principles of which he was one of the earliest and foremost advocates. Thus in 1884 he said: “With regard to the theory of evolution, I cannot help noting the wide toleration which has been infused into the public mind since the appearance of Mr. Darwin’s Origin of Species in 1858. Well do I remember the cry of anguish and detestation with which the views of Mr. Darwin were assailed when they were first enunciated. To one example of this I will here refer. There was a meeting of the British Association at Oxford in 1860, when the subject of the origin of species was discussed by the late Bishop Wilberforce. I was at a distance from the platform, my neighbours being for the most part clergymen. The vehemence with which the Bishop’s powerful sarcasm was cheered was extraordinary; and knowing full well that he would be effectually answered by a friend of mine, I was not able to forecast the consequences. But whatever these might be I was determined to share them; so I gradually edged my way through the crowd, overturning in my passage a seat on which many people were standing, till I got close to my friends, who, I feared, incurred some risk of a physical mauling. But the discussion passed away without violence, and in virtue of that plasticity with which the human mind in the long run takes the stamp of truth, those who were then so perturbed in spirit are now ready to admit, not only that the origin of species did them no particular harm, but that they are quite prepared to accept its doctrine.” On the occasion in question the Bishop of Oxford stated that the greatest names in science were then opposed to the Darwinian theory, which was chiefly defended by Professor Huxley and Dr. Hooker.

In like manner Professor Tyndall was able to say in 1885 that the germ theory of infectious diseases had grown like a mustard tree in his time. “I remember,” he said, “the time when it was referred to as an extravagant absurdity, but far-seeing men saw its final triumph. Now I suppose there is hardly a scientific physician in Europe that does not hold the germ theory of disease. In 1873 cases came before me of men suffering from intermittent or relapsing fever, and I longed to examine their blood; for it is a small spiral-looking organism in the blood that is the cause of relapsing fever. In 1876 Professor Cohn, of Breslau, was in this country, and he handed me a memoir that marks an epoch in the history of the subject with which it dealt. It was called in England the wool sorter’s disease, or splenic fever. It was sometimes also called Siberian plague. The paper had been drawn up from his own experiments and observations by a perfectly unknown physician, who held a small appointment in the neighbourhood of Breslau. The investigation impressed me as masterly in execution and as pregnant in result. The writer followed with the most unwearying patience and the most consummate skill, the life history of bacillus anthracis, which is the contagium of splenic fever. I said at the time this young man will soon find himself in a higher position, and next time I heard of him he was at the head of the Imperial Sanitary Institution of Berlin. That young man was Dr. Koch, who succeeded in detecting the living organism and in proving it to be beyond all doubt the veritable cause of the disease. Some years ago I paid a visit to a laboratory in Paris where I was shown by Pasteur himself, who verified Dr. Koch’s results as to the parasitic origin of splenic fever, this formidable bacillus anthracis, and it was curious to reflect how a thing so truly mean and contemptible should have such power over the lives of brutes and men.”

A report published in 1886 of examinations made by Dr. Miquel of the bacterial condition of the air at Paris and Mountsouris disclosed some remarkable facts. He stated that in the Rue de Rivoli the average number of bacteria in a cubic metre of air during the year 1881 was 6,295, whilst in 1884 the average number was only 1,830—a diminution which he attributed to the better draining and scavenging of the city. In the same period the deaths from zymotic disease in Paris showed a decrease of 27 per cent. The air over the Atlantic Ocean and on the top of high mountains showed only one to six bacteria per cubic metre. Such investigations are now recognised as a special department of science.

Some reminiscences which Professor Tyndall gave in 1880 of Thomas Carlyle showed his sympathetic appreciation of literary as well as scientific excellence. He exhibited the “sage of Chelsea” in a more favourable light than some of his literary friends have done. “It has been said that in respect to science Mr. Carlyle was not only incurious but hostile. This does not tally with my experience,” says Professor Tyndall. “During the lifetime of his wife and afterwards I frequently saw him, and as long as his powers continued unimpaired I do not remember a single visit in which he failed to make inquiries both regarding my own work and the general work of science. In physical subjects I never encountered a man of stronger grasp and deeper penetration than his. During my expositions, when these were clear, he was always in advance of me, anticipating and enunciating what I was about to say. He not unfrequently called to see me in Albemarle Street, and on such occasions I usually described to him what I was doing there. When I was engaged on the ‘chimera’ of spontaneous generation, I took him into my warm room, and explained to him the part played by the floating matter in the air in the phenomena of putrefaction and infection. He was profoundly interested, and as docile as a child.