It is only within the past few years that photography has been applied to astronomical development. In this connection, more accurate results are obtained by measuring the photographs of stellar spectra than by measuring the spectra themselves. Photography with modern rapid plates gives us, with a given telescope, pictures of objects so faint that no visual telescope of the same size will reveal them. It is in this way that many of the invisible stars have impressed themselves upon exposed plates and given us a vague idea of the immensity in number of those stars which we cannot view with eye or instrument. Though we have made great advancement, there are many problems yet even in regard to our own little system of sun worlds which clamor loudly for solution. The sun himself represents a crowd of pending problems. His peculiar mode of rotation; the level of sunspots; the constitution of the photospheric cloud-shell, its relation to faculae which rise from it, and to the surmounting vaporous strata; the nature of the prominences; the alternations of coronal types; the affinities of the zodiacal light--all await investigation. A great telescope has recently shown that one star in eighteen on the average is a visual double--is composed of two suns in slow revolution around their common center of mass. The spectroscope using the photographic plate, has established within the last decade that one star in every five or six on the average is attended by a companion so near to it as to remain invisible in the most powerful telescopes, and so massive as to swing the visible star around in an elliptic orbit. The photography of comets, nebulae and solar coronas has made the study of these phenomena incomparably more effective than the old visual methods. There is no longer any necessity to make "drawings" of them. The old dread of comets has been relegated into the shade of ignorance. The long switching tails regarded so ominously and from which were anticipated such dire calamities as the destruction of worlds into chaos have been proven to be composed of gaseous vapors of no more solidity than the "airy nothingness of dreams." The earth in the circle of its orbit passed through the tail of Halley's comet in May, 1910, and we hadn't even a pyrotechnical display of fire rockets to celebrate the occasion. In fact there was not a single celestial indication of the passage and we would not have known only for the calculations of the astronomer. The passing of a comet now, as far as fear is concerned, means no more, in fact not as much, as the passing of an automobile.