ABSTRACT
When, in speaking of the infinity of the different circles described by the different circular sections of the cone as you roll it on a plane round its vertex (9i4a5 -u ), the writer says that ‘they are all described by one and the same straight line', i.e. by all the different points on that line, the phrase is not strictly accurate. It is true that the circles described on the plane are the same as those which would
he described by (points on) one straight line equal to one of the 'generators’ of the cone; the describing line, however, is not one all the time but is continually changing. As the cone rolls, all the generators one after another, come into contact with the plane; but as they are all of the same length the effect is the same as if they were all one. This explanation is in essence quite clear. Only the wording is in some places strange.
