Foul air is the leading cause of tubercular and scrofulous consumption, so very common in our country. Dr. Guy, in his examination before public health commissioners in Great Britain, says: “Deficient ventilation I believe to be more fatal than _all other causes_ put together.” He states that consumption is twice as common among tradesmen as among the gentry, owing to the bad ventilation of their stores and dwellings. Says Dr. Dio Lewis, whose labors in the cause of health are well known: “As a medical man I have visited thousands of sick-rooms, and have not found in _one in a hundred_ of them a pure atmosphere. I have often returned from church doubting whether I had not committed a sin in exposing myself so long to its poisonous air. There are in our great cities churches costing fifty thousand dollars, in the construction of which not fifty cents were expended in providing means for ventilation. Ten thousand dollars for ornament, but not ten cents for pure air! “Unventilated parlors, with gas-burners, (each consuming as much oxygen as several men,) made as tight as possible, and a party of ladies and gentlemen spending half the night in them! In 1861, I visited a legislative hall, the legislature being in session. I remained half an hour in the most impure air I ever breathed. Our school-houses are, some of them, so vile in this respect, that I would prefer to have my son remain in utter ignorance of books rather than to breathe, six hours every day, such a poisonous atmosphere. Theatres and concert-rooms are so foul that only reckless people continue to visit them. Twelve hours in a railway-car exhausts one, not by the journeying, but because of the devitalized air. While crossing the ocean in a Cunard steamer, I was amazed that men who knew enough to construct such ships did not know enough to furnish air to the passengers. The distress of sea-sickness is greatly intensified by the sickening air of the ship. Were carbonic acid _only black_, what a contrast there would be between our hotels in their elaborate ornament! “Some time since I visited an establishment where one hundred and fifty girls, in a single room, were engaged in needle-work. Pale-faced, and with low vitality and feeble circulation, they were unconscious that they were breathing air that at once produced in me dizziness and a sense of suffocation. If I had remained a week with them, I should, by reduced vitality, have become unconscious of the vileness of the air!”