The old world and the new are alike affected by such obliteration. Long ago London took the lead with fogs proverbial wholly due to smoke, fine particles of solid matter in suspension making these points of condensation about which water vapor gathers to form cloud. With the increase of smoke-emitting chimneys over the world other centres of population have followed suit till today Europe and eastern North America vie with each other as to which sky shall be the most obliterate. Even when the obscuration is not patent to the layman it is evident to the meteorologist or astronomer. By a certain dimming of the blue, smoke or dust reveals its presence high up aloft as telltalely as if the thing itself were visible. Some time since the writer had occasion to traverse Germany in summer from Göttingen to Cologne and in so doing was impressed by a cloudiness of the sky he felt sure had not existed when he knew it as a boy. For the change was too startling and extensive to be wholly laid to the score of the brighter remembrances of youth. On reaching Cologne he mentioned his suspicion to Klein, only to find his own inference corroborated; observations made twenty years ago being impracticable today. Two years later in Milan Celoria told the same story, the study of Mars having ceased to be possible there for like cause. Factory smoke and electric lights had combined to veil the planet at about the time Schiaparelli gave up his observations because of failing sight. With a certain poetic fitness the sky had itself been blotted just at the time the master’s eye had dimmed. America is not behind in this race for sky extinction. In the neighborhood of its great cities and spreading into the country round about the heavens have ceased to be favorable to research. Not till we pass beyond the Missouri do the stars shine out as they shone before the white man came. Few astronomers even fully appreciate how much this means, so used does man get to slowly changing conditions. It amounts, indeed, between Washington and Arizona to a whole magnitude in the stars which may be seen. At the Naval Observatory of the former sixty-four stars were mapped in a region where with a slightly smaller glass one hundred and seventy-two were charted at Flagstaff.