Extracts from reminiscences of Mrs. Ayrton by A. P. Trotter, past President of The Institution of Electrical Engineers (London), (...-... .).

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On Herta Ayrton as a student

Hertha Marks, of Jewish parentage, was one of those women who can pass the Cambridge Little Go after a few months' coaching instead of grinding for years over elementary classics like boys at public schools. She told me that she never regretted the time and trouble of acquiring a smattering of Greek, and agreed that the true object of a 'pass' examination is to discover the capability of acquiring knowledge quite apart from the value of that knowledge. From her youth she had many well-known literary friends.

On her marriage and work on the electric arc following that of William Edward Ayrton

Hertha Marks, who had already made the acquaintance of Prof. Ayrton, began to attend his lectures and laboratory in the autumn of 1884, and they were married in the spring of the following year.

During the Chicago Electrical Conference of 1893, a Negro servant lighted a fire with a paper written by Ayrton on "Variation of Potential Difference of the Electric Arc with Current, Size of Carbons, and Distance apart". No rough copy or even an abstract existed of the paper which had not been read in full, and had described an unfinished and inconclusive research. ... Ayrton had investigated the behaviour of the arc by slowly varying the current between limits for many hours at a time, in fact, often for the greater part of a day. The unhappy arc never had a chance of settling down to adjust itself to any particular current, and looped curves were the result. Mrs. Ayrton, by patient hand control, kept an arc under a steady current for more than an hour at a time, and arrived at a constant definite voltage, or potential difference, as Ayrton called it. She obtained consistent results, expressed them, first in plotted curves, and then as equations, and interpreted the work of previous investigators. ... Her results were published in The Electrician and afterwards in book form in 1902.

On the behavior of electric arcs in powerful searchlights

Professor Ayrton had been requested by the Admiralty in 1903 to investigate the strange behaviour of electric arcs in powerful searchlights. "The four reports submitted to the Admiralty in 1904 - 8 were treated officially as his, although Mrs. Ayrton had assisted greatly in drawing up the three earlier reports, and the fourth was actually sent in over her own name because it embodied her unaided researches, and Professor Ayrton insisted that this should be made clear when it was forwarded to the Admiralty. The official mind, however, seemed unable to grasp that the work was not really done by the man who had been commissioned to do it; and perhaps it is unreasonable to expect too much of the official mind ... the fee was sent to her husband" -- quotation from Evelyn Sharp's Memoir of Hertha Ayrton; emphasis ours.

Carbon manufacturers with whom Mrs. Ayrton was in frequent communication recognized the importance of her improvements. She was consulted by a cinematography company who wished to avoid the sputtering and hissing of small arcs. The behaviour of cored positive carbons in which a pith of soft material burns away and helps to hollow out the crater was well known to her, and she had used cored negatives. But a negative, having no light-emitting crater, should be pointed. Sometimes carbon is deposited on it from the positive, giving rise to irregular "mushrooming". She made experiments to improve the pointing of the negative, and, contrary to all practice, she made soft negatives with hard cores and patented the invention shortly before the War. The result was a practical success, but arc lamps are now being superseded, not only in cinemas but in street lighting by improved incandescent lamps.

On conditions of the "hissing" arc

In my investigation on the rotating arc I had observed and avoided this stage ... The references in her book were most kind, and she presented some of my points more correctly and lucidly than I had done. In reply to my letter congratulating her on the publication of her book, and calling attention to a slip, she wrote, "... Your experimental comparison of the light of the arc and the area of the crater visible, and your proof of the connection between the two, was a very valuable bit of work, [of] which, I am sure you will allow I have made the fullest use, and I hope I have clearly expressed my great admiration of it as well ... It is a great relief to be rid of the book at last - sometimes I used to think it never would be finished, and that when I died I would order the single word 'Arc' to be placed on my tombstone as a pathetic record of my sufferings". She little knew what sufferings some of her future work would bring.

One of the conditions of the steady burning of the arc is the shape assumed by the ends of the carbons. A large square-ended carbon takes twenty minutes or more to settle down quietly after hissing, or rather roaring. She found that by properly shaping the ends, the arc was in good order a few seconds after recarboning.

Acting on this, the Admiralty and War Office standardized the carbons used for searchlights [which] had long before used small negative carbons in order to avoid the shadow cast by them. The limit of their size was their fragility, and sometimes they were run nearly red hot. Mrs. Ayrton suggested that they should be coppered to carry the current, and this was adopted both by the Admiralty and by the War Office. Soon after her death in 1923 I spoke about her work to a Royal Engineer Officer. He was contemptuously incredulous that a woman could have had anything to do with search lights. He had probably never seen any other kinds of carbons.

Her paper on "The Hissing Arc" was read before the Institution of Electrical Engineers, of which she was elected a Member, in 1899. ... It was rather unfortunate that she gave [it] the title "The Hissing of the Electric Arc". Those of her audience who had anything to do with arcs knew that they sometimes hissed and gave reduced light, but few of them attached much importance to it. For the London Press the important thing was that a woman should address an audience of engineers. She was described as "a little dark-haired, dark-eyed lady, wearing pince-nez, who created a sensation which perhaps accounted in some degree for the unusually large attendance of young men members" ... (emphasis ours).

On her study of sand ripples

The wrinkles and ridges of sand on the sea shore attracted her attention and scientific inquisitiveness. They bear some resemblance to the ripples on the surface of a liquid, but are obviously of a different nature. A long and intricate research was undertaken, and in publishing the results she decided to call them ripples. Vaughan Cornish had carefully studied, described and photographed waves of water, sand and snow, but that was not enough for Mrs. Ayrton. Like young Clerk Maxwell, she wanted to know "What's the go 'o that?". Cornish had made world wide observations. For Mrs. Ayrton a couple of square yards on the Margate shore sufficed.

I have only a copy of the first of her Royal Society papers to refer to, and a few of her letters to me, and will not go into details, but I cannot forget the beautiful experiments which I have watched. After her husband's death she turned the large drawing-room of her house at 41 Norfolk Square into a laboratory, and equipped it with glass tanks. Some were a yard long and about ten inches wide and deep, filled with water, and a layer of sand about an inch deep on the bottom. They were mounted on rollers and moved to and fro to make waves swing backwards and forwards. Some were kept in motion by electric motors.


As I have said, mathematicians had busied themselves with theoretical waves and vortices. I do not know if Mrs. Ayrton found that her practical observations conflicted with their rigorous results; probably not. When they were offered to the Royal Society, criticisms were raised, and she was sensitive about them, for there was an apparent conflict. Her paper was rejected by the referee; but Lord Rayleigh entered the lists, championed her cause, her paper was accepted, and the Hughes gold medal was awarded to her for this and her work on the electric arc (emphasis ours). They accepted several other papers from her.

... she investigated the movements of water, and contributed to the Société Francaise de Physique a paper on the formation of sand ripples and on the internal movements of water. To write the paper in French and fluently to deliver it in that language was no difficulty, nor was the transport of the glass tanks and other apparatus and the performance of the experiments a task beyond her powers, but a long paper on a very different subject was on the programme, and she was nearly crowded out. Such experiments as time permitted went off well, her interpretations were received and cordially appreciated, and the President said that in this race between experimental and theoretical science theory had for the present been overtaken, even existing mathematics were not able to deal with the subject, which remained to be explained by les mathématiques de l'avenir.

An application of importance - the Ayrton fan.

... her investigation of the production of sand ripples may be said to have been the outcome of scientific inquisitiveness; but she turned it to an application of great importance at that time, in the War [WWI]. Those who saw her experiments at home or the results at the front cannot forget them, but few of the younger generation have heard of them, and that is why, admiring her work as I do, I will put my recollections on record. Early in 1915 the Germans with fiendish brutality began to use poison gas. She thought that eddies of air might be used to repel gas attacks. ... The Ayrton fan was quite capable of rolling it back in the open, and, unexpectedly, even I think by Mrs. Ayrton, of clearing dugouts into which gas had fallen.

An historical account of the of the Aryton fan.