This brings us to the planet’s albedo, which Müller at Potsdam has found to be 75 per cent. Now the interest attaching to this determination is twofold, that it bespeaks cloud and that it seems to imply something else. The albedo of cloud is 72 per cent of absolute whiteness. What looks like cloud, then, is such, on that distant disk. But Jupiter surpasses cloud in lustre, since his albedo exceeds 72 per cent. Yet a large part of his surface is strikingly darker than that. The inference from this is that he shines by intrinsic light, in part at least. The fact may not be stated dogmatically, as there is no astronomic determination so uncertain as this one of determining albedoes, and therefore Herr Müller’s results must be accepted with every reserve, but they suggest that Jupiter is still a semi-sun, to be recognized as such by light as well as heat, though his self-luminosity, if it exist at all, can hardly exceed a dull red glow. [Illustration: I. JUPITER AND ITS WISPS.—A DRAWING BY DR. LOWELL, APRIL 11, 1907.] [Illustration: II. JUPITER AND ITS WISPS.—A DRAWING BY DR. LOWELL, APRIL 11, 1907.] [Illustration: S. N. PHOTOGRAPH OF JUPITER, 1909. P. L.] A modern detection on Jupiter’s disk has been that of wisps or lacings across the bright equatorial belt, a detail of importance due to Mr. Scriven Bolton. Requested to look for them, the observatory at Flagstaff was not long in corroborating this interesting phenomenon. The peculiarity about them pointed out by Mr. Bolton is that they traverse the belt at an angle of about 45° to the vertical, proceeding from caret-shaped dark spots projecting into the bright belt from the dark ones on either side. They exist all round the equator and are found indifferently dextrous or sinister—sometimes vertical. For there are others that go straight across. Nor are they confined to the bright equatorial belt, but are to be seen traversing all of the bright belts both north or south up to the polar hoods. From its sombreness it seems that we are here regarding a phenomenon in the negative; remarking it by what it has left behind, not by what it has accomplished. For the wisps are not wisps of cloud, since they are dark, not light, but gaps strung out in the clouds themselves.