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.

The distance apart of such shafts would largely depend on the size of them, but as a rule it will be found that house owners object to large pipes, in which case the number must be increased, and if we take a distance of about 30 yards, we should require about 5,000 such shafts in Leicester.  Whether some artificial means of inducing currents in sewers by drawing down fresh air from shafts above the eaves of the houses, and sending forth the diluted sewer gas to still higher levels, or burning it in an outcast shaft, will take the place of natural ventilation, and prove to be less costly and more certain in its action, remains to be seen.  But it is quite certain that notwithstanding the patents which have already been taken out and failed, and those now before the public, there is still a wide field of research before this question is satisfactorily solved, so that no cause whatever shall remain of complaint on the part of the most fastidious.