American Scientist

To the Editors:

Henry Petroski’s article about slide rules (“Slide Rules: Gone But Not Forgotten,” Engineering, May–June) certainly struck a number of resonances with me. As a budding science and math enthusiast in the early 1960s, I received a Keuffel and Esser Log Log Duplex Decitrig slide rule as a gift from my parents. I marveled at the large number of scales that allowed one to do a host of different types of calculations.

It was very useful to me a few years later as an undergraduate chemistry major. However, when I took the physical chemistry laboratory course in fall 1965, a higher precision was required in calculations, so we were given access to a Friden desk calculator in the lab. I still remember the extended chunk-a-chunk-a-chunk sound that this heavy machine made when one had to divide two numbers. Later on in my undergraduate career, when I had to do my senior thesis, we were allowed to use one of the first electronic calculators, manufactured by Wang Laboratories. It was a huge device, or so it seemed, and it was mounted under a desk in a small calculations room. The display, which sat on the desktop, was an array of nixie tubes, and calculations were carried out quickly and noiselessly.

Later on, during my graduate-school years, the first handheld scientific calculators appeared. I remember my research advisor proudly showing us his HP-35, which at the time (about 1972) sold for $395. When I departed for my postdoctoral position, I purchased an HP-55 for about $250; it had the advantage of being programmable. Soon after, I started teaching undergraduates in the mid-1970s, and my colleagues and I had a debate as to whether the general chemistry students should be allowed to use calculators on exams. An older colleague insisted on picking “easy” numbers for the quantitative problems so that students without calculators could do the math in their heads (assuming they remembered the multiplication tables). By the late 1970s the cost of the scientific calculators had fallen to the $20–$30 range, and we were soon able to convince him that it would be all right to allow the students to use them.

Thank you for an interesting article that allowed me to indulge in a bit of nostalgia.

Henry C. Brenner
New York University (Retired)
Brooklyn, NY