The report of last year of a committee of the metropolitan board of works is worth attention, as showing the opinion of metropolitan surveyors. Out of forty districts, the opinions of whose surveyors were taken, thirty-five were in favor of open ventilation, two were doubtful, two against, and one had no experience in this matter. The average distances of the ventilators were from 30 to 200 yards, and the committee came to the conclusion that "pipe ventilators of large section can be used with great advantage in addition to, and not in substitution for, surface ventilators." To supplement the street openings as much as possible with vertical cast iron or other shafts up the house sides would seem to be the first thing to do, for there can be no doubt that the more this is done, the more perfect will be the ventilation of the sewers. It must also not be forgotten that the anxiety, of late years, of English sanitarians to protect each house from the possible dangers of sewer gas from the street sewer has led to a system of so-called disconnection of the house drains by a water seal or siphon trap, and that, consequently, the soil pipes of the houses, which, when carried through the roofs, acted as ventilators to the public sewers, have been lost for this purpose, and thus the difficulty of sewer ventilation has been greatly increased. In Leicester we have been fortunate enough to secure the co-operation of factory owners, who have allowed us to connect no fewer than fifty-two chimneys; while we have already carried out, at a cost of about L1,250, 146 special shafts up the house sides, with a locked opening upon a large number of them, by means of which we can test the velocity of the current as well as the temperature of the outflowing air. The connections with the high factory chimneys are all of too small a caliber to be of great use, being generally only six inches, with a few exceptionally of nine inches in diameter. The radius of effect of specially erected chimneys, as shown by the experiments of Sir Joseph Bazalgette, and as experienced with the special ventilating towers erected at Frankfurt, is disappointing and discouraging when the cost is taken into consideration. It can not be expected, however, that manufacturers will admit larger connections to be made with their chimney; otherwise, of course, much more satisfactory results would be obtained. To fall back upon special shafts up the house sides means, in my opinion, that there should be probably as many in number as are represented by the soil pipes of the houses, for in this we have a tested example at Frankfurt, which, so far as I know, has up to the present moment proved eminently satisfactory.