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Professor John Perry (1850-1920), electrical engineer and mathematician
1850 Born on 14 February at Garvagh, Co. Londonderry, second son of Samuel Perry.
1860 School in Belfast (1860–64).
1864 Apprentice in the drawing office and pattern shops of the Lagan foundry of Coates Ltd in Belfast; attended evening classes.
1868 Won a Whitworth exhibition; returned to full-time education, studying engineering at Queen's College
1870 Graduated early with first-class honours, a gold medal, and the Peel prize, followed soon afterwards by a Whitworth scholarship.
1871 Taught physics and mathematics at Clifton College, Bristol,
1874 Honorary assistant to Professor Sir William Thomson (Lord Kelvin) at the University of Glasgow.
1875 Professor of civil engineering at the Imperial College in Tokyo. Collaborated with W. E. Ayrton publishing many papers (chiefly on electrical subjects) in British scientific journals.
1879 Returned to London. Married Alice (d. 1904), the daughter of Thomas Jowitt of Sheffield.
Employed to reorganize the machinery of Clark and Muirhead's telegraphic works
1881 Worked for the City and Guilds Institute as its national examiner in mechanical engineering.
1882 Appointed professor of mechanical engineering at Finsbury Technical College
Ayrton and Perry collaborated, until about 1889, in a number of electrical inventions, including the electric tricycle, the ameter and voltmeter. Achieved several patents and worked as consultants for the Faure Accumulator Co, arranged the lighting of the Grand Hotel at Charing Cross, and, with Fleeming Jenkin, co-founded the Telpherage Co to exploit their patents for transporting goods by wires, which came to be widely adopted in the USA.
1896 Appointed Professor of mathematics and mechanics (to 1913) at the Royal College of Science and School of Mines in London
1904 Became general treasurer of the British Association for the Advancement of Science
1920 Died suddenly at home in London
1920 Obituary 
JOHN PERRY, M.E., D.Sc, LL.D., F.R.S., died in London on the 4th August, 1920.
Every electrical, in fact every engineer, must mourn the death of Perry ; but as he was a Past President of the Institution, and personally known to most of us, his loss touches us deeply.
He was born in 1850, in Belfast; and he had practical engineering experience, and was also a keen student. He gained a Whitworth Exhibition which enabled him to get college training. He was appointed Physics Master at Clifton in 1870. It was here I first saw him. I remember the first time I heard him lecture, and his luminous treatment of mass and gravity, which put into words the reason why a heavy stone could be thrown higher against air and gravity than an empty ball - a point one never could explain in words as a child, though understanding the matter in the sort of way a dumb animal may grasp things. His lectures fired all the boys who had any scientific leaning with tremendous enthusiasm.
Tilden came as Chemistry Master a few years later ; and with the same power of inspiring the students. Perry was very young, about 21, and had some difficulty in preserving order. Once he had a mouse to illustrate something in electrostatics; but the discharge of a Leyden jar killed it before its experiment was due. The whole "set" immediately gave vent to howls and groans of "Cruel Mr. Perry!" "Who killed the mouse?" while Perry kept trying to explain that he never meant to hurt it. Boys used to ask leave to go out: they would play fives for ten minutes or so, and come back. One day the applications were too numerous even for Perry; so he snapped out: "You may not. You should go out before you come in." It is said that once, to save time, he said : "I will not call all the names over ; all absentees hold up their hands."
After Clifton, Perry went to Sir W. Thomson in Glasgow, and thence to Japan. There he and Ayrton did a tremendous amount of work, mostly electrical. Many years afterwards I was telling him a story about Captain Cardew, who sat with Major Marindin, holding an inquiry about 1889. I had given evidence that Ferranti's Deptford cables must have a leakage capacity current of about an ampere ; and this was what was disturbing the Post Office telephones. Cardew asked me to see him after the hearing, and said : "I do not get quite the same result; how did you make your calculation? "I said the calculation was quite simple; what result did Cardew get? He admitted it was not "quite the same as mine." I found Cardew had forgotten v2, the ratio of the electrostatic and electromagnetic capacities ; and his leakage current was 900 million billion amperes. Perry looked sad and said : "Why do you tell me that story? Ayrton and I made the same mistake in Japan, and Maxwell never let us hear the end of it."
There is so much of interest in Perry's life that it will be best to concentrate on his influence on electrical engineering, more especially as other aspects of his work have been fully treated in various notices that have already appeared. As a teacher at Finsbury, and in South Kensington, his ability in clear explanation and his personal enthusiasm and influence can best be measured by the extraordinary success of City and Guilds students in the profession, many of them owing a great deal to Professor Perry.
As inventors, Ayrton and Perry were very active from about 1880 to 1885 or 1890. Of the partners it is clear Perry was the chief inventor. I do not remember whether Perry or Thomson invented the ohm-meter. The voltmeters and amperemeters with permanent magnets and specially shaped pole-pieces were very useful in the early eighties. From a modern point of view they were very poor; but there was nothing better to be had then. The twisted-strip instruments followed. The idea was most ingenious and very original. Certainly the instruments absorbed so much power that when dealing with low pressures, or small currents, it was better to use the voltmeter to measure current, and the amperemeter for low pressures. All the same they were most valuable, and much needed.
The most important inventions were motor and clock meters. These were long before their time. Ayrton and Perry's pendulum instrument was the original of modern clock meters ; and it was designed to measure ampere-hours, or watt-hours. The motor meter was the ancestor of those now in use. If a contact switch for cutting cells in and out of a battery makes contact with two blocks, it short-circuits one cell ; if it leaves one contact before touching the other, the circuit is broken. Perry invented the pilot contact with a resistance. On the other hand, Ayrton and Perry were the chief upholders of the fallacy that the design of a motor should be quite different from that of a dynamo. It was not until Mordey published an article in the Philosophical Magazine that this heresy was killed.
For the last 30 years Perry did little in the way of inventing, though recently he turned his attention to the improvement of the gyrostatic compass. He was an expert in the theory of spinning tops. Probably the way a top always moves at right angles to the direction one wants it to go, appealed to him as an Irishman.
About 1890 he had a collection of tops arranged to illustrate, somehow, Maxwell's electromagnetic theory of light; and his "Spinning Tops " is a delightful work.
Professor Perry was always an active member of the Institution, of which he was elected a Member in 1878, and in conjunction with Ayrton he read many papers ; also he often joined in discussions. He was President in 1900-1901. Personally he was a splendid, warm-hearted Irishman ; perfectly straight, and transparently honest. Ireland has given us more than her share of men with high mathematical powers and original minds. He was always genial, and full of humour ; and he never had, or could have an enemy in the world. He was a Whitworth Scholar (1870), F.R.S. (1885), also a D.Sc. and LL.D.
His best-known books are "Steam"; "Applied Mechanics"; "The Steam Engine"; "The Calculus for Engineers"; and "Spinning Tops." He has also done yeoman work in the improvement of education, especialty as regards mathematics
1920 Obituary