Excerpt from Zenographical Fragments II: The Motions and Changes of the Markings on Jupiter in 1888

There is, however, one correction which it does seem desirable to make here. In Volume I., pp. 112 and 113 and elsewhere, the fact that the white equatorial spots were frequently accompanied by a white spot nearly Opposite to them in the great rifts of the equatorial belts was considered to show that the equatorial spot and the companion spot in the rift were really one spot apparently divided into two by the overlying dark belt; and as a corollary that the white spots were at a lower level than the dark belts. Subsequent Observations, however, made under better conditions, have shown that the equatorial white spots commonly communicate with the bright spots in the rifts by means of real and comparatively narrow channels or canals. The appearances suggest rather that the white material breaks through the dark material of the belts, than that it extends under the latter. The probability is that the upper surfaces of both the white spots and the dark belts are actually at nearly the same altitudes. This subject is only just mentioned here, for the evidence upon which this conclusion is based is derived chiefly from the Observations of subsequent years, made when the planet was in a much better position for Observation than it was in either 1887 or 1888. It is here sufficient to merely state the fact that I no longer consider that the white spots extended under the dark belts.

There is a mingling both Of pleasure and regret in publishing a series of Observations made many years previously. On the one hand, there is satisfaction in the thought that the work of reduction and discussion has been better and more thoroughly done than would probably otherwise have been the case. On the other hand, there is a mingling of regret, for one feels sometimes that the Observing work might have been done better than was actually the case, if only the observer could have set about it in the light of his present knowledge.

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