Cyril Catt has 550 slide rules, give or take a few. And quite a number of abacuses too. He has big slide rules that hang on the wall, for school use. Small ones to put in your pocket. Round ones. Slide rules from around the world. And he’s always on the lookout for more.

These vintage devices, so vital for engineers and scientists before the invention of the electronic calculator, are practically redundant, but their elegance and ingenuity charms many collectors who, like Cyril, scour garage sales and antique shops for interesting examples to enjoy, use and share.

Every collector has a story about how they came to their hobby. Cyril’s story starts during World War 2. But to get to that beginning you have to start a lot earlier, with his father and with World War 1. Cyril’s dad, George, was just a lad in that war, growing up in England. There were food shortages and George often went on excursions to the countryside to get fresh produce from his great aunt’s small farm. While visiting his aunt, he encountered a substantial number of botany books in the library of his great uncle, an accomplished gardener. A remarkably intelligent lad, George absorbed a great deal of knowledge about horticulture and with that knowledge he managed to get a position as a foreman gardener at an English “great house” and this in turn led him to a horticultural course at Kew Gardens.

Next, George was head-hunted by the American United Fruit Company for a management job at a plantation in Costa Rica. He, his wife Violet and their young daughter Ruth were in Jamaica when the Great Depression hit and forced them home to England where, in due course, George wound up as estate manager for a film studio at Denham, working for movie-maker Alexander Korda (later to be knighted for his services to the film industry).

When World War 2 arrived (now we get to meet Cyril, who had been born in 1935) many British children were sent from the cities into the country to get them out of danger. Considerable numbers were also sent overseas and Alexander Korda – who had worked in Europe and later Hollywood before moving to England – arranged to have his nephew sent to the USA and George and Violet Catt sent their children too. The children had been staying at charitable accommodation, linked to the film industry, known as the Actors’ Orphanage, along with about 60 others. They were all evacuated to the USA in September 1940.

Cyril was only five and Ruth a few years older when they were sent by train to Glasgow and put aboard the ship – Cyril recalled it was the Empress of Australia – for the voyage to the United States via Canada. It was a hazardous trip – not that the children knew it at the time. Another ship carrying children to presumed safety, the City of Benares, was sunk by a German submarine on September 17, 1940, with terrible loss of life.

After a train trip from Quebec to New York, Cyril and Ruth were separated, each going to different host families. Cyril has fond recollections of his first host family, whose now grown-up son’s bedroom featured an electric model railway and scores of books to read.

After spending time with those families Ruth and Cyril were sent to another in Cincinatti, Ohio, where they stayed on a rural property outside of town. It was here that one of Cyril’s tasks was to milk the house cow and wash out the milk separating equipment, a task that was to have unforeseen consequences in years to come. It was at the local school that Cyril saw his first slide rule. It was love at first sight. “I was shown how to use a slide rule for multiplication and I thought this was a wonderful shortcut,” he recalled. His host “father” ran an electronics business in Cincinatti, and sometimes he took Cyril there. Again, Cyril saw engineers and others using slide rules and the usefulness of these remarkable tools was reinforced in his mind.

How Cyril and Ruth got back to England in 1945 is a long story. To cut it short, his father had been assigned a posting in Istanbul in the early stages of the war and Violet had accompanied him there, also finding a job. The time arrived when Violet decided it was time to collect her children and take them home. This was easier said than done. Violet had to travel by train to Cairo and fight for a place on a ship from there to the USA. As it happened, her cabin-mate was the Persian bride of a US serviceman who was struggling with a newborn baby. Cyril’s mother was able to help this woman enormously and was repaid when it emerged that the woman’s new father-in-law was an influential Democrat politician who was able to help Violet locate and contact her children.

“I’ve never lived down my reaction to her first telephone call,” Cyril laughed. “She spoke like a BBC announcer and I said ‘My, what an accent!’ in my own acquired Bronx accent.”

Cyril’s father was contractually bound to remain in Istanbul until 1946, so his mother took Ruth and Cyril – after some time spent waiting for a ship – from the US back to England via Halifax, Canada. They arrived home in early 1945. Cyril recollected seeing one of the ships in their convoy strike a mine in the Irish Sea, and he was shocked when he saw the damage caused by intense German bombing raids to the city of Liverpool.

When Cyril’s father returned to England after the war he resumed his position under Alexander Korda who had a senior role with MGM British. George’s job was managing the substantial land-holdings of MGM, at a time when all holders of agricultural land were required to produce food for the war-torn and hungry nation. George also ran the greenhouse and nursery that supplied flowers and plants for the movie sets. According to Cyril, his father ended up being on the board of MGM Great Britain.

Now at boarding school, Cyril was getting good marks. But when he brought up the subject of slide rules he was advised by a master that such devices were “for artisans” and not really up to scratch at a posh school. At school Cyril was also troubled by very frequent and severe stomach upsets. Cyril said these attacks affected him for about five years until, when he was unable to collect a prize at a school presentation day, the chairman of the school’s board of governors – who happened to be Lord Horder, a leading member of the British Medical Association – delivered the prize to him in person and began an investigation into Cyril’s condition that culminated in a diagnosis of tubercular peritonitis – the bovine form – evidently contracted from raw milk at the farm in Ohio where he had stayed during the war.

At the time in Britain, the best available treatment for this condition was rest and whatever sunshine could be obtained, so Cyril spent 18 months in bed on a hospital balcony reading Biggles books and whatever other volumes he could get his hands on. At some point during his hospitalisation his father presented him with a small pocket slide rule and this fascinating instrument helped him while away some time. One of the nurses caring for him was a refugee from a Baltic state who had a good knowledge of mathematics. This nurse explained some of the more advanced functions of the slide rule and gave Cyril a crash course in trigonometry. He made a full recovery from TB, but trigonometry remained with him for the rest of his life.

After he finished school Cyril worked for a time on some farms before signing up for National Service and being sent to the Middle East as an aircraft wireless mechanic with the Royal Air Force, unluckily having his time extended by the advent of the Suez Crisis. After stints in the Canal Zone, at Malta, Aden and Cyprus, he went back to England and to horticultural jobs. He studied for a degree at Durham University’s Newcastle College but found there were no jobs available when he graduated. In 1963 he married his sweetheart, Sonja. The pair had met while working in a laboratory, separating blood products. Cyril landed an agricultural job in Western Australia and he and Sonja moved to Australia in 1964. Next he got a job with the Hunter Valley Research Foundation in NSW and the couple settled in the Newcastle suburb of North Lambton, building a house and raising a family. The rest of Cyril’s working career was spent with the NSW Department of Agriculture, under its various names and incarnations.

When he arrived in Australia Cyril owned only a small handful of slide rules. One he had used when he was an aircraft wireless mechanic was a five-inch pocket model with an “addiator” on the back. This was a useful scale for additions and subtractions. In Australia he had discovered Japanese-made circular sliderules which he found perfect for keeping in his shirt pocket when visiting farmers in the course of his work. “I also used to have a slide rule for currency conversions when we travelled,” he said. Once, in Hong Kong, a baffled vendor asked him where the batteries went.

It was probably about 1968 when, trailing after Sonja in an antique store in Brisbane, he spotted a vintage slide rule with unusual scales. He bought it to find out more about it and his collecting hobby was born. “At that point I knew very little about the history of slide rules and I didn’t realise there had been about 20,000 different models made,” he said.

The arrival of the first consumer electronic calculators in about 1972 was an exciting time. Cyril couldn’t wait to get his hands on one. But it also spelt the end for slide rules as a widespread calculating tool, since slide rules have many limitations that don’t apply to calculators. But that doesn’t mean slide rules don’t still have their uses. According to Cyril, some examples where slide rules still rule are calculating decimal powers and roots and in situations where you aren’t necessarily looking for a precise answer but are instead wondering if a certain thing is possible. “A slide rule can give you a sense of how much a thing misses by, because you are seeing a range of possibilities on the slide rule scale,” he said. That concept leads to “nomograms”, which Cyril used in his job to help farmers make decisions by helping them see the possible results of altering variables like quantity and cost of cattle feed when other factors like weight etc are taken into account. Cyril said these graph-like diagrams enabled farmers to get answers to complicated questions without having to perform calculations. (Nomograms are a fascinating field on their own, but outside the scope of this blog post.)

After decades of collecting, Cyril now has more than 500 slide rules, but he says many of them are duplicates he bought in the hope of trading with fellow collectors. These days, however, fellow collectors are not easy to find and their numbers are dwindling with the pool of people who used slide rules or even know what they are. He says there are about 30 slide rule collectors in Australia, but a great many more overseas. Some collecting clubs even produce regular magazines and newsletters, which Cyril eagerly receives. And time has not diminished his enthusiasm for finding new specimens.

“It’s been about 40 years since slide rules were widely manufactured,” he said. “And as people who owned them are dying off, their families tend to throw the slide rules away, not regarding them as having any value.”

Cyril and Sonja’s daughter, Karin Catt, is a noted photographer, with a long list of celebrity portraits to her name.

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