Unlike the elliptic trammel, only half an ellipse can be drawn with this device, making it a semi-elliptic trammel. It can be turned 180 degrees to draw the other half of the ellipse. Although this ...

But why have I linked these two items, the "do-nothing" machine and the ellipse? The answer is in the mathematical name for the machine: the elliptic trammel. That's right! The trammel is a device for ...