In discussing Howard’s discovery of the stages of cloud-formation we found something lacking, for it was clear that the three stages of cloud proper – stratus, cumulus and cirrus – have a symmetry which is disturbed by the addition of a fourth stage, represented by the nimbus. This showed that there was need for a fifth stage, at the top of the series, to establish a balanced polarity. We can now clear up this question of a fifth stage, as follows.