In the southern hemisphere the 24-inch Bruce telescope of Harvard College Observatory has obtained many very remarkable photographs of nebulæ, particularly in the vicinity of Eta Carinæ. But the great reflectors of the Mount Wilson Observatory, on account of their exceptional location and extraordinary power, have surpassed all others in the photographic portrayal of these objects, especially of the spiral nebulæ which appear to show all stages in transition from nebula to star. No less remarkable are the photographs of such wonderful clusters as Omega Centauri, a perfect visual representation of which is wholly impossible. Intercomparison of the photographs of clusters has afforded Bailey of Harvard, Shapley of Mount Wilson and others the opportunity of discovery that hundreds of the component stars are variable. What is the longest photographic exposure ever made? At the Cape of Good Hope, under the direction of the late Sir David Gill, exposures on nebulæ were made, utilizing the best part of several nights, and totaling as high as seventeen, or even twenty-three hours. But the Mount Wilson observers have far surpassed this duration. To study the rotation and radial velocity of the central part of the nebula of Andromeda, an exposure of no less than 79 hours' total duration was made on the exceedingly faint spectrum, and even that record has since been exceeded. The eye cannot be removed from the guiding star for a moment while the exposure is in progress, and this tedious piece of work was rewarded by determining the velocity of the center of the nucleus as a motion of approach at the rate of 316 kilometers per second. But when the stars, their magnitudes and their special peculiarities are to be investigated _en masse_, photography provides the facile means for researches that would scarcely have been dreamed of without it. The international photographic chart of the entire heavens, in progress at twenty observatories since 1887, the photographic charts of the northern heavens at Harvard and of the southern sky at Cape Town, the manifold investigations that have led up to the Harvard photometry, and the unparalleled photographic researches of the Henry Draper Memorial, enabling the spectra of many hundred thousand stars to be examined and classified--all this is but a part of the astronomical work in stellar fields that photography has rendered possible.