Dr. Small assigns to Franklin the credit of having discovered that repeated respiration imparts to air a poisonous quality similar to that which extinguishes candles and destroys life in mines and wells. "The doctor," he records, "breathed gently through a tube into a deep glass mug, so as to impregnate all the air in the mug with this quality. He then put a lighted _bougie_ (candle) into the mug, and upon touching the air therein the flame was instantly extinguished; by frequently repeating this operation, the _bougie_ gradually preserved its light longer in the mug, so as in a short time to retain it to the bottom of it, the air having totally lost the bad quality it had contracted from the breath blown into it." Upon being consulted with regard to the better ventilation of the House of Commons, he advised that openings should be made near the ceiling, communicating with flues running parallel with the chimneys and close enough to them to be kept warm by their heat. These flues, he recommended, should begin in the cellar, where the air was cool, and the flues being warmed by the hot air of the chimneys, would cause an upward current of air strong enough to expel the vitiated air in the upper part of the house. Franklin's letters at this time are full of the importance of ventilation. Unquestionably, he was among the first who called attention to the folly of excluding fresh air from hospitals and sick-rooms, particularly those of fever patients. As Mr. Parton expresses it, he cleared the pure air of heaven from calumnious imputation and threw open the windows of mankind.