Harold M. Mott-Smith

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Interviewed by
George Wise
Interview dates
March 1 and 2, 1977
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Interview of Harold M. Mott-Smith by George Wise on 1977 March 1 and 2, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/5043

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Deals mainly with his career at General Electric Company in Schenectady, NY. Early interest in science leads to first (summer) job at age 15, with Irving Langmuir at G.E.; comments on Langmuir's work. Undergraduate studies at Cornell University interupted by military service, 1918; switches from chemistry to physics at Cornell in 1919. Returns to G.E. in 1921; collaborations with Langmuir on, among other work, mercury arc rectifiers (plasma), space charge equations (leading to a Langmuir patent for the thyratron) hydrogen-welding (R. W. Wood). Comments on Langmuir as a scientist and as a co-worker (Katie Blodgett); ideas far ahead of his time: the linear acelerator, the neutron. Comments on Whitney as head of the Lab and on other members of the staff, such as Coolidge (who succeeded Whitney as Head), John Payne and Dewey Simonds (vacuum tube work). Work atmosphere at G.E.; outside activities. Leaves G.E. for Eidgenössische Technische Hochschule, Zurich, in pursuit of doctoral degree.


This is not a transcription of his remarks, but it is a rearranged paraphrase.

I was the chief assistant to Irving Langmuir in 1912, I came in to work for him for a summer, but mainly in 1921-1928.

I was born in France, and moved to Schenectady in 1907. My father was an artist. My mother was a Yates, which is a prominent family in this area.

I got interested in science through the following accident. While we were still in France, when I was seven years old, I came down with the measles. It happened that one of the books that was available to me was Gano’s(?) Physics. It was an excellent non-mathematical introduction to the subject, and I read it thoroughly. I decided that this was my particular bent in life.

My mother knew the Langmuirs socially, and she mentioned that I was interested in science. Langmuir suggested she send me down to the laboratory. Dr. Whitney was head of the lab then. The man who actually hired me was the chief engineer — Larry Hawkins. I was 15 years old then — this was the summer of 1912. I was given a test job, with the same salary as the test boys — I’m sure you know about the test program. I worked on the fourth floor of building 5.

When I went to see Langmuir, the first thing he did was to pull out a slide rule and slide it back and forth. “What’s the principle of this?” he asked. Well, even though I understood logarithms, and had worked with them, I didn’t know that this was an automatic way of using logarithms. So I flubbed the first question. But I guess I must have answered the other ones he asked, although I don’t remember them, since I did get the job.

One thing I remember about that summer was that I always used to watch out for the days when Dr. Steinmetz, or Dr. R. W. Wood — who was one of our consultants — would come to the lab. They both smoked big black cigars – and at that time there was a very strict rule against smoking in the laboratory. They’d come in smoking their big cigars. The guard would scowl at them, but there was nothing he could do about it.

I also recall that at the time I came, Langmuir was very excited about some X-ray breakthrough that had just been made. Nothing to do with Roentgen — this was the work proving that X-rays could be diffracted by crystals — the work of Von Laue. This was also about the time when Langmuir started the battle to prove to the Germans that he was right about the pure electron discharge. The ductile tungsten work had recently been done, and it was about this time that somebody discovered that thoriated tungsten — tungsten to which some thoria had been added, — didn’t offset. The thorium seemed to lubricate the motion of the crystals and allow them to move past each other.

When Langmuir had come down to the Laboratory, which was in about 1909, he was given the job of improving the life of the carbon lamp. When the tungsten lamp came along, that made things a lot easier. To improve the life, he had to find out what goes on inside a glass bulb with a filament in it.

He was one of the first people to realize that to get a really good vacuum, you had to heat the glass and drive off the gas. He was one of the first to get a good vacuum — one where the mean free path of the atoms was greater than the diameter of the tube or lamp. When he had the vacuum, he would put in hydrogen, and heat the filament. When he heated that tungsten filament, the hydrogen pressure went down. The atoms were disappearing in the glass walls. When he heated the glass walls, the hydrogen came back. He also began to coat the walls with various things, and he found that the metallic coatings he put on absorbed hydrogen.

Before this work, the bulbs were not heated in vacuum work (i.e., baked out).

This work later led to many more things. He had the cataclysmic idea that physical and chemical forces were the same thing. And he also proved that he could make a monatomic layer on the glass, and it was enough to entirely change the properties of the surface.

That summer I came, the diffusion pump was already available, but it was limited by the back blast of mercury, which got back into the space being pumped out. Langmuir’s contribution was simply to cool a surface to condense out the mercury vapor; that’s why the pump he made was called the condensation pump. He told me all this — that a cooled glass surface would completely absorb the mercury vapor. Then he wanted to show me the equipment.

He had taken a big kitchen boiler, capacity about 100 gallons, and had it cleaned up, and heated, and fixed onto a vacuum system. “Now you, Mott-Smith,” he said, “will find the speed of this pump.” First we had the boiler pumped out with an oil pump. There was a MacLeod gage attached, and it still showed something in the tank. Then the condensation pump was attached, and pumped it out. Within two minutes the MacLeod gage registered zero!

When I went off to college — I went to Cornell — I didn’t come back to the Laboratory in the summers. I had gotten two or three scholarships to go to Cornell. I found the work there hard on my eyes, so I remember I used to take the summers off and go up to Maine.

When I was at Cornell, I remember that I couldn’t keep an interest in some of my classes. So, even though I had these scholarships, my record wasn’t very good. I had some other problems also. I had come to understand the big contribution that Steinmetz had made, which is, of course, the application of complex numbers to transmission line calculations. I had learned his formulas, and when I was at Cornell, I used them to solve one of the problems I was given. The professor gave me a zero! He didn’t understand what I had done. Steinmetz was still that far ahead of the universities even as late as his, which was 1916 or 1917.

I was in the class of 1918, but, as I said, I had some troubles. For example, we had a course in the Corliss engine, or some such thing, and I couldn’t get interested in it, so I didn’t do the report and didn’t pass. The dean then was pretty hardboiled; as a result of all this they didn’t give me my degree in 1918. Then the war came along, and I went into military service.

It was during the war that I me Mr. Alexanderson. The New Brunswick transmitter was being hooked up by Alexanderson. I could drive a car, which was not so common in those days as it is now. So I was hooked by Alexanderson.

One of our jobs was to test the Beveridge antenna. This was a great big long thing. We were doing the tests down in New Jersey. We laid out the antenna one day, and up comes the sheriff of the county, who was about to arrest us. “I didn’t know that you weren’t German spies,” he said to us after we had explained to him what we were doing.

But we got into even worse trouble when we drove into Asbury Park on a Sunday. Asbury Park is the most religious place in the country. One of their laws was that no vehicle could be driven there on a Sunday. So here I come driving in and they arrest me and take me off to the jail. I nearly got put into jail. It took one of the biggest GE lawyers to pay my bail and get me out.

After the war, in 1919, I went back to Cornell. I had previously been a chemistry major. I was interested in organic chemistry, which I thought was going to be a big field. Professor Brown, in the chemistry lab, had noticed my aptness in chemistry. He told Professor Richtmyer, in the physics department, about me, Richtmyer said “why don’t you come over and do some physics with me?” Then his fellows told him that I was pretty good.

So after the war I came back and spent a year or two getting my degree in physics. I got a darned good education in classical physics. I learned some statistical mechanics, which came in handy much later. I worked out a theory of the shock wave many years later, when I was with the AEC. This became a pretty famous paper.

Anyway, the whole story shows the kind of thing that can happen at some universities. The dean at Cornell just wanted to turn out the kind of people who would make good chemical analysts, as they called them in those days. They were interested in having their people get jobs — not in having people with original ideas.

You could say that Langmuir asked me to come back from Cornell and work for him. Actually, I think that Richtmyer wrote to Langmuir and mentioned me. Langmuir had a succession of people who were able to solve problems for him in mathematical physics. He never went much for doing mathematics himself, although, of course, he always understood the significance of it.

When I got back in 1921, Katie Blodgett was his secretary. She told me about his trouble with the everlasting law suits — that was the famous high vacuum tube case. And he had also developed thoriated tungsten, the basis for the 200-1-A tube that was very successful for GE.

I’ve mentioned that Langmuir originated the theory that physical and chemical forces were one and the same. This was in the heyday of colloid chemistry. A man named W. D. Bancroft at Cornell was the biggest colloid chemist in the country. He was also a big stockholder in the copper mining business. I remember that when Langmuir announced his theory, Bancroft was supposed to have said: “if Langmuir is right, then catching a fish is a chemical reaction.”

It was about in 1921 that Langmuir began to ask me to make molecules with COH or COOH groups, and a long hydrocarbon chain attached. One of them was based on oleic acid. A monolayer of these on a glass surface would change the whole adsorption properties of the glass. The acid end would stick to the glass.

About the time that I came back to GE, in 921, the word came down from on high that they wanted some developments based on the mercury arc rectifier. Langmuir and I went to work on this, studying are discharges.

Langmuir noticed a certain uniformity in these discharges — a uniform glow modified by sheaths over the cathode and over the anode — the one over the anode was harder to see. Langmuir was the one who originated the name “plasma.” I’ve told this story in my letter to Bueche.

Kenneth Kingdon later said that Langmuir had the right idea when he picked that name. He said tha tin the blood you have red and white corpuscles, and you also have germs. Well, we ran into “germs” with our plasmas too. They were the little electropositive particles that got into the tube and gave us so much trouble.

For a long time, the rest of industry and the universities regarded “plasma” as a special GE patent term, and they wouldn’t use it. But finally it was applied in the thermonuclear fusion work, which was government supported. When someone on government support called it a plasma, it was OK.

Names were important for patent protection, of course. De Forest called his tube an Audion to fix it in peoples’ minds that this was something new and different. And GE did the same thing with the name “pliotron,” and the rest. It’s not the fellow who invents the thing that matters; it’s the one who names it.

Langmuir sometimes told me just what to do; but a lot of the time he left me to my own devices.

I am a mathematical physicist. In 1923, I think it was, I had worked out the space charge equation with both kinds of ions present, and I wanted to prove that my equations were correct. To prove my equations, I had a special tube made up. It had a specially heavy tungsten filament, and a grid around the filament made of unusually thick wires, spaced so that the distances between the wires was less than the diameter of the wire. I had the whole thing mounted so that I could look down from the top and see the sheaths around the grid wires. The sheath is the dark space around the wires — an indication that there is only one kind of charged particle present, since the light in a discharge tube is given off by the recombining of ions and electrons.

As I made the grid more and more negative, the sheaths grew, and deformed, and eventually blended together. This shut off the discharge. I could start it again by raising the voltage.

I said(?) all of this to Langmuir, and of course he was very interested.

That same after I discovered that he was there talking to a lawyer. “You have suggested a great idea to me,” he said. That same afternoon, he and the lawyer began writing out a patent application. The application was in Langmuir’s name, not in mine. This didn’t bother me. I hadn’t seen the practical significance of it, so I wasn’t upset about not getting the patent. I had only been interested in proving out my theories, and showing that the sheaths would grow in the way that I had predicted. I was only interested in the mathematical result.

So this was the thyratron. The method of control by having the sheaths come together was used for some time, although it was later replaced by phase control. I had thought that Langmuir had thought up the name “thyratron,” but it may very well be that Hawkins made up the name, as it says there (in James Cobine’s introduction to a volume of the Langmuir Collected Works).

You ask why the mercury rectifier was important to the higher ups in the company at this time? DC current h ad a tremendous application in the metallurgy of copper, and other metals.

And there was another idea in view. Langmuir may have suggested it. If we could make a rectifier, then we could make its inverse — an inverter. Langmuir was interest in DC transmission, which you could do if you had a rectifier and an inverter. But Westinghouse beat us out with their “tickler” to convert DC to AC.

In 1928, Dr. Whitney took the plasma work away from Langmuir and Mott-Smith and gave it to Hull. We had been paying too much attention to the science, and not enough to the engineering problems. For example, a metallic enclosure requires an insulator. How the heck do you seal it in. We hadn’t even considered [???] the late 1920’s — you could look the details up in the European literature.

When the plasma work was taken away from us and given to Hull, Langmuir and I felt a little bit… we laughed at ourselves, we realized that the laboratory had to move ahead to engineering.

Hydrogen welding was another case of the same kind. Langmuir had found that a tungsten filament would dissociate hydrogen into atoms, and that the atoms would recombine at any metal surface. A long time after that — during the time that I was at the laboratory — R. W. Wood of Johns Hopkins wrote a letter to Langmuir. He had built a geissler-type tube with two electrodes in it, and, for some reason I don’t recall, a third electrode sticking into the middle. He filled the tube with pure hydrogen, and set a glow discharge. He examined the light given off spectroscopically. Near the ends of the tube he got the band spectra of molecular hydrogen. In the middle of the tube he got the line spectra — Balmer lines — of atomic hydrogen. But then he noticed that the electrode stuck into the middle of the tube was glowing white hot. What was happening?

This is what he wrote to Langmuir to find out. I was there the day that Langmuir got the letter. Right off the bat, Langmuir figured out that the hydrogen atoms were recombing at the middle electrode, and giving off tremendous amounts of heat there. And right off the bat he figured — that’s a hell of a good way to selectively heat a piece of metal.

That very afternoon he had a blowtorch man in. He had set up equipment so that atomic hydrogen was striking a piece of metal in a crucible. Only the metal was getting hot. He had the blowtorch man — the welder — try it out.

Now Langmuir was interested in this because he thought it was a good way to heat metal without the container, the ceramic crucible, getting heated. But the welder noticed something else — that he could get clean welds without flux. And this was the thing that really turned out to be important about hydrogen welding. This was the beginning of gas shield welding.

One thing about Langmuir. He was a little bit hesitant — or what I really mean to say is adjustable about giving credit.

One time he wrote a paper and put my name on it. He thought I deserved the recognition. Later, after I had developed some important formulas and published them, he took the same formulas and put them in that famous Tonks and Langmuir paper.

It was the same thing with some of the surface chemistry experiments. He decided that Katie Blodgett should have some credit, so she got the credit for the films.

Also, to a certain extent he was neglectful. He didn’t read the literature to the extent that he should have. For example, Child had developed the space charge equation before Langmuir, although he only treated the case of positive ions. Langmuir should have looked this up in the literature and given the credit — but he didn’t. I think one of the reasons that he didn’t read the literature as thoroughly as he might have was that he was so far ahead of the others.

I’m sure there was nothing deliberate about the way that he took the credit for some things that he shouldn’t have. He wouldn’t take the credit if he knew what the others had done. He wasn’t that kind of a man.

I never found Langmuir cold or unfriendly. He would talk to anybody. As a result, he was exposed to fellows who wasted his time. Eventually, Katie Blodgett and I formed what we called the “Langmuir protective society.” You see, Langmuir had an office about the size of this one (about 200 sq. ft.) and he didn’t even have an anteroom. Anyone who wanted to could just walk right in and start talking to him. Katie Blodgett and I would talk to the people who came in. If it was somebody who had some kind of a crackpot idea — somebody who didn’t have much to offer Langmuir — we would turn him away.

Doctor Whitney came to our laboratory often. One thing I remember about Whitney. When I came to the Laboratory, I asked Whitney what I was supposed to do. “You do whatever Langmuir wants you to do,” Whitney said. “And what does Langmuir do?” I asked. “He does whatever he wants to do,” Whitney answered. “My job is protecting him from the top side.”

Whitney knew that if you had a genius, you could say “leave him alone.” Whitney gave a free hand to people like Langmuir. We were allowed to stick to the scientific end of things. If anything, we didn’t keep enough track of what the other people, like Westinghouse, were doing.

Langmuir never discussed salary or business matters with me. I don’t know how it worked regarding salaries. I got increases. I imagine that Whitney made the recommendations, and he told Hawkins, who worked out the details. I never heard Langmuir say one word about any of this.

Langmuir was interested in the patents, though. I think that he considered it his responsibility to turn out something valuable for GE. But I never heard him talk about how much money one of his inventions had made the company, or anything like that.

Whitney gave Langmuir a free hand. But he also knew when to take work away from somebody — like the plasma work he took away from us — and he recognized when new people were needed. This was shown with his importation of the chemists. I’ve discussed this with Charlton. So many of the top people he brought in were chemists — Langmuir, Dushman, Coolidge, Whitney himself, Marshall. He may have thought that chemists were closer to the practical applications — physicists were one step further away.

Whitney established the whole chemical department at the Laboratory. One possible reason for this was that the mining industry had walked right off with Langmuir’s ideas about floatation, and hadn’t given GE anything. Another important thing at that time was the Emmett mercury turbine, where they needed some sensitive means of detecting leakage.

Whitney abolished red tape. There wasn’t anything we couldn’t get. For example, platinum wife — you just had to go down to the stock room and take it. I’d go down to the stock room for something, and say “Langmuir wants it.” And, of course, after a while they knew that I worked for Langmuir. I never had to use a shop order for anything in my life.

There wasn’t the least bit of resentment in the laboratory about Langmuir’s freedom and privileges. It’s true that many of the others had to stick more closely to the Company businesses. But Langmuir always told the others what he was doing. He always shared his ideas.

The others — Hull, Dushman and Coolidge — didn’t have the serendipity that Langmuir had. They couldn’t see the relationships among the scientific principles in the same way that he could.

Coolidge was more of a development engineer type of person. He was good at carrying through his ideas, and making something practical out of them. It was always clear to us that Coolidge would be the next director. He was on good terms with everyone. He didn’t have the chance to get out into the labs as much as Whitney did. And he was quiet and reserved. But he was friendly and got on well with everybody.

Since the Research Laboratory was right down at the Works, I had a lot of contact with the other operations of the company. I used to go across the street to the Standardization Lab quite often, to see what was going on there. I got a real education in what was really happening in the company. Also, Langmuir used to take me down to the big shops, especially the turbine shops. He told me all about the big Swede that was in charge of the engineering there (Junggren).

Speaking of the Swede reminds me that one day in the laboratory I saw posted a memo from somebody up high in the organization — a vice-president, I think — addressed to Whitney. It made quite a point of the fact that practically all of the top technical men in the company had been trained abroad. It listed the head of DC motor design, whose name I can’t recall; and the man I mentioned from turbine; and, of course, Langmuir and Whitney; and a lot of others. It was true. At that time there wasn’t the level of accomplishment in our schools that there was abroad. I’m not sure if the memo was intended to make us feel good, or to encourage better education here in the United States. I think part of the idea was: “have we got to stand for this sort of thing.” (that is, does the U.S. have to depend on Europe to educate its brightest people.)

I’ve mentioned the freedom that Langmuir was given. But when there was a real problem, he turned out just like anyone else. For example, in 1927, I think there was a problem with the Monitor Top refrigerator. We called it the “constipated refrigerator” — it seemed that the refrigerant, SO2, reacted with the water released from heating the mica insulation to form sulfuric acid, which ate away at the wire insulation.

When this happened — it was just before I left the lab — Whitney called a meeting of the whole staff in Rice Hall. The engineers from the Refrigerator Department came in and told us about the problem.

They turned out the whole Lab for that one, including Langmuir. He made no fuss about that. He had turned out on one thing after another to help out the Lab.

Another side of Langmuir was the ideas he had that were way ahead of the times. I remember that he had the whole idea of the linear accelerator — using radio-frequencies, and keeping the cycles in just the right phase — all worked out. This was before 1928, when I left. He had no idea of a use for it — he just found it to be an interesting idea.

He also got the idea of the neutron at about the same time. I remember him telling Kenneth Kingdon and I about it. He was inspired by the results Aston had gotten — the Aston number. He tried to get us interested.

You ask why the lab didn’t get into nuclear physics at this time? We couldn’t see any particular connection between it and the company’s businesses.

Langmuir didn’t have much interest in the quantum theory, which was being developed so rapidly at about that time. Dushman was the only one interested in it. I explained part of it to him – the use of Hamilton’s operators, in a more generalized way than they were used to classical mechanics.

I wasn’t really involved in the radio work that went on during the 1920’s. The main people who I remember working on that were John Payne, who was a wonderful mechanic, and Dewey Simonds. They went to work on the vacuum tube. Simonds invented the first 4-element tube, with a space-charge grid. He showed it to Whitney, and he was told — by the radio people — “put it in the cooler — we’ve got to get rid of the 200-1-A’s.” So Philips came out with the four element tube first, and beat us out of the business.

Simonds died not long afterwards, of Hodgkins’ disease. It may be that after he died, they had to get the patent in somebody’s name, so they got the four-element tube patent in Hull’s name. I’m not too sure about this, though.

John Payne was a mechanic who could not only grind valves — which all of us who owned cars could do in those days — but he also could grind cylinders, which was a rarer talent. Every spring, when all of us were putting our cars into shape, we’d do the dirty work on his car in exchange for getting him to work up ours.

Another thing we set up was the skate-sailing club. Langmuir had showed this to me at Lake George. After I told Payne about it, he got a sailmaker at the Works to make sails for all of us — Company expense. We’d take them up to Lake George. You could really get going on that ice — up to 40 miles an hour, I’m told, although I never went quite that fast.

Another recreation we had was music. Lewis T. Robinson, the head of the Standardization Lab, was a great lover of music. He organized a band that I played in.

In 1928 I left the laboratory to get my doctor’s degree at the ETH in Zurich. I didn’t want to leave. I was proud of the fact that I was about the only scientist at the lab who wasn’t a doctor who was publishing real scientific papers.

I left at the suggestion of Dr. Whitney. He said to me that while I was doing good work, I just couldn’t fight the establishment, and I would need that degree to get ahead.

So I went to the ETH, and got my degree there. And after I finished, Loomis at Illinois offered me a job. So I was a professor for seven years. And then the OSRD got me, and I took on the job of demagnetizing ships. There I was, an unworldly professor, bossing a lot of gobs around.

I never did get back to being a professor.