Boy and man, to use a quaint old expression, I had had a friendly interest in Chimney Swifts (Chktura pelagica) for years before I had opportunity to observe one of their retiring drills. In August, 1922, a group gathered at one of the tall old chimneys in a house near the Governor's mansion in Columbia, S. C. My work carried me out of the city the next day, and I was gone for several days. Ten years later, almost to the day, I found another such band wheeling about the chimney of Christ Episcopal church in this city. For several days I had excellent opportunity to study their movements. The advance of twilight brought out the gathering chippers, though one evening they began more than half an hour before sun-down. Swifts collect by hundreds in a formless mass, then perhaps they dart away for a number of blocks, form a long line like a letter I and advance on the chimney that is to be their host. Coming near the leaders veer to the right or left and draw the line into a J, at times perhaps reversed. The tail curls into a circle, and the whole band presents the appearance of a script figure of 6, also perhaps reversed, the tail being wound rapidly on the revolving loop to form an O. This ring may grow wider or contract, and often a few birds lead off to the outside and are followed by a trail that for an instant gives the whole group the appearance of a small Greek delta, S, then if all follow, in another instant we have an S; then quickly the upper loop closes into a new circle on which the lower part of the S is rapidly wound, and soon a counter-clock revolving ring has given place to one turning clockwise. But all the individuals may not follow. Sometimes enough remain in the old circle to keep it going, the neck of our small delta turns upon itself and strikes back upon the first ring and quickly we have a figure of the two loops revolving in opposite directions, one on the other like cog-wheels! The law that drives vortices in a particular direction on a particular side of the equator cannot tyrranize over the Swifts. Once only a crowded 10 (with the 1 apparently crushed against the 0) was seen; better say a small alpha, a, or a mathematical node. The birds seemed to sweep in at the upper tab, swing round the loop and emerge at the lower tab. This gave place to a sort of double ring or figure of 8 with segments dropped from each loop in such a way as to produce a fleeting figure of 3, but so rapidly was all this done that the eye could not record with accuracy the processes involved. The absence of the involved figures is noticeable during the last days of their performance, but this may be no more than coincidence.