Of these double stars with complementary colors we quote the following from Professor Dunkin (who, in turn, quotes from Admiral Smyth, the author of "Sidereal Chromatics"): "In Eta Cassiopeiæ the large star is a dull white and the smaller one lilac; in Gamma Andromedæ, a deep yellow and sea-green; in Iota Cancri, a dusky orange and a sapphire blue; in Delta Corvi, a bright yellow and purple; and in Albiero, or Beta Cygni, yellow and blue. In most of the remaining stars of the list the contrasting colors are equally marked, and also in many others which are not included in it." Some of these double stars are variable in their colors, as are the ordinary single variables, and, of course, for a similar reason,--to wit, the varying intensity of more or less cumulative planetary impacts. The interpretation, of course, as explained below, is that these suns, each one of different mass and consequently of different electrical resistance, are arranged in parallel circuit along a single line of electric current; a pair of different-sized arc or incandescent lamps, similarly arranged, would exhibit precisely the same phenomena. A compound solar system of this sort, apparently, with double sun and single planetary system in process of formation, nearly completed from a spiral nebula, is shown in a gaseous nebula within the constellation Ursa Minor, illustrated in Lord Rosse's drawing (see Nichols "Architecture of the Heavens," Plate X., lower figure). More than three thousand of these binary stars have been catalogued, and some of them make a complete revolution about their common centers of gravity--so distant are they from each other--in periods of not less than sixty, or even eighty, years. Of the double star Mizar,--the middle one of the three which form the tail of the Great Bear,--Professor Ball states that, by new methods of spectroscopic analysis, the component stars which form this double have been found to be one hundred and fifty millions of miles apart, while Alcor, a smaller star, visible to the naked eye, and enormously farther from Mizar than are the components of the latter from each other, moves through space in a parallel direction and with the same velocity as its double companion. What the connection may be, if any, we do not know, but their identical course is obviously related to some common circumstance of origin, as is the probable case with those other groups of stars which drift through space together. They show that solar systems are not necessarily individual creations, but may be formed in groups at the same period of time, and by the operation of natural laws simultaneously directed upon or into the creative matter from which solar systems are built up and sent along their way. It has been already shown that our sun has a motion around the center of gravity of our own solar system, as a whole, similar to that of the binary stars around each other, but that, by reason of his vast