Of Slide Rules and Jalousies
Jun. 10th, 2004 08:16 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
stoutfellowYesterday, in Math 400, we advanced to the time of John Napier, the discoverer of logarithms. I discussed other, earlier methods of simplifying calculations by turning multiplications into additions, and then went on to the line of thought Napier followed in developing the (more efficient) method of logarithms. This led naturally enough to a discussion of the slide rule. Lo and behold, one of my students actually had seen one! (She's a schoolteacher, and one of her elderly colleagues hung one in the classroom.) I explained why they worked and showed them mine, demonstrating various operations. (Mine's a nice one from the mid-to-late '60s, a 21-scale log-log model. Memory fails me, but I may have inherited it from my brother. It was only a bit later - 1970 or '71 - that I got my first electronic calculator. It was rather large - larger than a paperback novel by Robert Jordan - and could add, subtract, multiply, and divide.)
I let them spend the second and third hours working on problem sets. I gave one group the task of understanding multiplication by the gelosia method and division by the galley method. The text gave them a worked example of each, but did not give general instructions; their task was to work another example of each, and then explain why the methods worked. Gelosia is so called because it involves drawing a picture which vaguely resembles a jalousie (gelosia in Italian, or so I understand). It's quite a clever method; its biggest disadvantage is that, yes, you have to draw a picture which vaguely resembles a jalousie. I told them that, if they thought hard about how decimal notation really works, they should be able to figure out gelosia - and they did! I'm quite proud of them. (I don't know if they got a handle on the galley method; they have a week to put together the writeup.) (I set the other group to solving cubic and quartic equations by 16th-century methods. They needed a hint or two, but got the job done too.)
So I'm pretty pleased tonight.
I let them spend the second and third hours working on problem sets. I gave one group the task of understanding multiplication by the gelosia method and division by the galley method. The text gave them a worked example of each, but did not give general instructions; their task was to work another example of each, and then explain why the methods worked. Gelosia is so called because it involves drawing a picture which vaguely resembles a jalousie (gelosia in Italian, or so I understand). It's quite a clever method; its biggest disadvantage is that, yes, you have to draw a picture which vaguely resembles a jalousie. I told them that, if they thought hard about how decimal notation really works, they should be able to figure out gelosia - and they did! I'm quite proud of them. (I don't know if they got a handle on the galley method; they have a week to put together the writeup.) (I set the other group to solving cubic and quartic equations by 16th-century methods. They needed a hint or two, but got the job done too.)
So I'm pretty pleased tonight.
