From this table it will be seen that the temperature of the sewer air averaged 2.7° higher than that of the atmospheric air. On 9 days only was the movement wholly up, on 185 days it was wholly down, and on 88 days intermittingly up and down. In October the difference in temperature was 8-40°; on two days only was the movement wholly up, and on the 8th, when the difference in temperature was 16.5°, there was no upward movement. This clearly shews that, whatever may be the cause of the movement of the air in sewers, temperature need not practically be considered.

Some further interesting experiments were also carried out by Sir J. BAZALGETTE and Col. HAYWOOD, with a view to ascertain whether it was possible to drive air through a sewer of great length; when they found any attempt to force air through a sewer 400 yards long was not practicable. Only under the most favourable circumstances will the air

travel over 200 yards. This was again confirmed by Mr. SANTO CRIMP at Wimbledon, who had 620 yards of 12-inch sewer trapped off at the lower end. The difference in the level between the lowest and highest point was 100 feet. At the latter point was fixed a fan, all the ventilators in the sewer to be experimented upon were closed except the one at the foot of the hill, which was an air shaft. The fan was, theoretically, equal to changing the air of the sewer once in five minutes, and, before it was set going, air was found to be steadily passing down the sewer. On its being set to work as an extractor, the air still steadily passed out at the foot of the hill, not at all affected by the powerful exhaust at the top.

ALFRED KING, Fellow.

NOTE B.

There is so little debatable matter in the Paper itself that it is only possible to speak on its title, the one or two practical works referred to being of such a character that they can scarcely be looked upon as examples in the matter of ventilation; and, seeing that these references were almost entirely to drain and sewer ventilation, much better conclusions could have been deduced from the valuable experiments made by Mr. SANTO CRIMP at Wimbledon.

The great difference between house-drain and sewer ventilation has been shewn to be that, whereas house drains are more readily ventilated upwards, or with the air current passing in an opposite direction to the flow of sewage, sewers lend themselves to a system of downward ventilation with the air and sewage flowing in the same direction, and any attempt to pass air upwards through a sewer, even though aided by powerful fans and exhausts, has been proved a failure for any considerable length, the air current induced by the sewage flow being too strong to be so overpowered.

There is little doubt that the most efficient method of ventilating sewers would be that in which the sewer could be divided into short lengths, say, of 70 to 100 yards, by means of air traps, without interfering with the flow of sewage every section to have an opening at each end, a continuous current of air being maintained by the flow of sewage, which would probably be little affected by wind or other circumstances.

In house drains the conditions are different. The flow of sewage is not continuous, and with a ventilated soil pipe at the head of the drain, particularly where the building is high, upward ventilation is imperative, for it is not wise to advocate the carrying up of a second ventilating shaft to the roof from the lower end of the drain, on account of the counteracting influence it would have on the provision of a continuous through current. Although it is the theory that these twin shafts each act as inlet and outlet in turn, the air current is necessarily feebler and is not maintained in one direction long enough to change the air in the drain, the consequence being that impure air is wafted about in the middle portion of the drain's length until some occasional influence, such as the passage of a large volume of water, expels it.

The mica valve in the inlet box is somewhat in the nature of a necessary evil, but it is absolutely indispensable in positions where the sudden puffing out of foul air caused by a heavy flush would be objectionable or dangerous, which is nearly always the case in town houses. Where an open situation can be secured for the fresh-air inlet it is better without a valve, not only as regards its interference with the air current, but also because sometimes the state of high pressure in a drain, caused by the sudden discharge of a volume of water, particularly from a closet at the top of a high soil pipe, will occasionally force the water seal in traps

near the lower end of the drain, unless such a safety outlet is afforded.

While, perhaps, the principle of flow of air in a drain system is not altogether that of the syphon inverted, it is impossible to agree with the speaker who denied the existence of the syphonage system at all. In water syphonage, the difference in weight of the two columns causes the downward flow of the heavier; in the air syphon the circumstances are reversed, and the result is the upward flow of the lighter, the superior weight causing its ascension being that of the outside air. That it is possible for this action to take place in one material, as air into air or water into water, may be readily proved by the laws governing the fluids. The air in a drain is invariably of different temperature to the outside air, the difference being greatest in cold weather, and, warm air being less dense and consequently lighter than cold air, the theory of the discharge of a fluid into another of similar density and weight (which, we will admit, is impossible by syphonage) is disproved. With regard to the ventilation of rooms, there is certainly a real benefit accruing from a systematic heating of the incoming air, chiefly, in this country, from the drying action exercised. We in our damp and foggy climate know only too well that the moister the atmosphere, the greater is its power of holding dirt, soot, and other impurities in suspension; and, in order that the full benefit in this respect should be derived from heating the incoming air, the heating chambers should be of sufficient size to allow the air to be passed through at a low velocity, and so permit of the deposit of impurities before the air is taken into the building. Such a system was installed some years ago for the warming and ventilation of the German Houses of Parliament. While, therefore, the stoves mentioned by Mr. PILDITCH enabled a difficulty to be overcome, it is evident that the velocity of the incoming air through

the tubes would be too great to allow of the deposit of impurities, with the consequence, especially in foggy weather, that the particles of dirt and soot would be carried by the quick current into the apartment, and deposited on the furniture and decorations as soon as the current of air had sufficiently lost its velocity.

H. G. ASSITER, Professional Associate.

On Mr. Douglas Walker's Paper on "Rights of Way."

("Transactions," Vol. XXV., pp. 35-46.)

NOTE A.

Mr. DOUGLAS WALKER'S Paper on this subject will no doubt be of considerable assistance to the members of our profession, but I regret that the learned author should have thought it desirable to abstain from citing some of the cases on which he relied for his arguments.

I am quite in accord with Mr. S. B. SAUNDERS, who stated that twenty years was not sufficient to give an indefeasible title. It must be longer than that. See Sec. 2 of the 2 and 3 William IV., c. 71. This is a point on which I think the author might have thrown some light in his reply.

This point was brought prominently before me some years since in connection with a property consisting of a shop at Deptford, with side passage affording an additional entrance to the garden at the rear. At the end of the garden was a plot of ground, separated from it by a fence, and being practically land-locked. The owner claimed a right of way over our garden and through the passage into the street. Various acts of aggression on his part necessi