A faint straight-edged beam of light, or “sheath,” accompanied the comet, enveloping the head and projecting like a hood three or four degrees in front. Besides this, three or four irregular shreds of cometary matter were detected, escorting the comet, as it were, like airplanes, at a distance of three or four degrees when first seen, but gradually receding from it, and at the same time growing fainter. The actual length of the comet’s train at one time exceeded one hundred million miles, more than the distance of the sun from the earth. (If the head of the comet had rested on the earth, and its train stretched outward toward the sun, it would have extended seven million miles beyond that luminary.) The trains of comets have been grouped under three types, _viz._, the long straight rays as shown in the photograph of Halley’s comet, though this was only one of the many outlines assumed; the second is the curved, plume-like train resembling that of the comet of Donati; and thirdly the short stubby brushes violently curved. The great Daylight comet had a greatly curved train belonging to the second type, and it was mainly composed of carbon compounds. The curvature of the train was due to matter for which the repulsive force is only a fraction of the gravitational force. The pressure of light from the sun was a most important factor in the formation of its train. When the fierce pressure of the sun’s light strikes upon the particles forming the train, it drives the particles which are of the same relative size as the particles of light along with them, just as when the waves of the sea break against a beach they tend to drive small pebbles and sand upward along the beach. HINTS FOR AMATEUR PHOTOGRAPHERS To an amateur photographer who desires to obtain the picture of a comet which may appear perchance in the near future, their capricious appearance at unexpected periods being one of their charms, the following hints may be most acceptable. For work of this kind an equatorial telescope is used with a photographic lens and camera strapped thereon. The telescope is mounted on an axis that is parallel to the earth’s axis, and is made to rotate westward by what is called a driving-clock just as fast as the earth turns to the east. It will follow the motion of the sky (which apparently drifts westward), and keep every star approximately fixed in the field of view, or on the photographic plate in the attached camera.