Page:The evolution of worlds - Lowell.djvu/200

164 A side-light is cast upon the Jovian state of things by the "great red spot," which has been more or less visible

for thirty years, and which takes five minutes longer than the equatorial band to travel round. Its tint bespoke interest in what might be its atmospheric horizon. Yet it betrayed no sign of being either depressed or exalted with regard to the rest of the surface. "In 1891," as Miss Clerke puts it, "an opportunity was offered of determining its altitude relative to a small

dark spot on the same parallel, by which, after months of pursuit, it was finally overtaken. An occultation appeared to be the only alternative from a transit; yet neither occurred. The dark spot chose a third. It coasted round the obstacle in its way, and got damaged beyond recognition in the process." It thus astutely refused to testify.

Now, this exclusiveness on the part of the "great