'For years past I have recommended the adoption of such ventilating chimney openings as above described, and I devised a balanced metallic valve, to prevent, during the use of fires, the escape of smoke to the room. The advantages of these openings and valves were soon so manifest, that the referees appointed under the Building Act added a clause to their bill, allowing the introduction of the valves, and directing how they were to be placed, and they are now in very extensive use. A good illustration of the subject was afforded in St James's parish, where some quarters are densely inhabited by the families of Irish labourers. These localities formerly sent an enormous number of sick to the neighbouring dispensary. Mr Toynbee, the able medical chief of that dispensary, came to consult me respecting the ventilation of such places, and on my recommendation had openings made into the chimney flues of the rooms near the ceilings, by removing a single brick, and placing there a piece of wire gauze with a light curtain flap hanging against the inside, to prevent the issue of smoke in gusty weather. The decided effect produced at once on the feelings of the inmates was so remarkable, that there was an extensive demand for the new appliance, and, as a consequence of its adoption, Mr Toynbee had soon to report, in evidence given before the Health of Towns Commission, and in other published documents, both an extraordinary reduction of the number of sick applying for relief, and of the severity of diseases occurring. Wide experience elsewhere has since obtained similar results. Most of the hospitals and poor-houses in the kingdom now have these chimney-valves; and most of the medical men, and others who have published of late on sanitary matters, have strongly commended them. Had the present Board of Health possessed the power, and deemed the means expedient, the chimney openings might, as a prevention of cholera, almost in one day, and at the expense of about a shilling for a poor man's room, have been established over the whole kingdom. 'Mr Simpson, the registrar of deaths for St Giles's parish, an experienced practitioner, whose judgment I value much, related to me lately that he had been called to visit a house in one of the crowded courts, to register the death of an inmate from cholera. He found five other persons living in the room, which was most close and offensive. He advised the immediate removal of all to other lodgings. A second died before the removal took place, and soon after, in the poor-house and elsewhere, three others died who had breathed the foul air of that room. Mr Simpson expressed to me his belief that if there had been the opening described above into the chimney near the ceiling, this horrid history would not have been to tell. I believe so too, and I believe that there have been in London lately very many similar cases.