« EelmineJätka »
quality of the water in order to re-assure the said public that the water they were drinking was beautiful, they found Dr. Odling himself saying that it was not a reliable test. Yet at the end of the paper he said London water was very superior because of this very thing, for he brought no other evidence. That appeared to his mind very unsatisfactory, speaking not as a medical man, but as one of the long suffering public who had to drink water which had been testified to be contaminated, not far from the intake of the companies, with organic matter of the foulest description. It was true those cases were not very flagrant, except at particular periods, but they wanted a guarantee that they should not occur at all. What was the use of talking about filters, and telling the public the water was unfit to drink unless it were filtered. It was the grossest cruelty to the poor. They could not buy filters, and even if they were distributed gratuitously, there was not one family in ten who would take care of them, so as to see them renewed. You might filter out the cats and dogs, and the grosser particles of matter ; but the better the filter the sooner it became filled with germs, and every kind of contamination. It was the very nature of a filter to become filled with foulness, to breed microbes, to become itself a source for contaminating the water, if it were not renewed within a reasonable time. The gentlemen who spoke so much in favour of filtration had an idea, which was good in itself, that the filtering medium should be so arranged as that it could be renewed; but to say that the general public were to depend on any kind of filter, paten or not, was stark nonsense. This evil was not imaginary, for it was given in evidence before the Metropolitan Medical Commission in 1830, that whenever water was contaminated so as to be nauseous, diarrhæa was invariably prevalent, and affected the health of every person drinking it. He did not want to increase the cholera scare, but he hoped to utilise it, by demanding of the authorities that no money should be spared to give a good supply of water, which should be available for every house in the city, without putting a single inhabitant to the expense of a filter.
Dr. ODLING, in reply, said he had been invited to read a paper on the chemistry of water, and had, therefore, confined himself mainly to chemistry ; and for this, under the circumstances, he did not think he was to blame. At the same time he might say that for many years he was a medical officer of health, and had since attended to hygienic studies, and he came prepared to speak not only as a chemist, but also as a physician and hygeist. As regarded the general question, the influence of the presence of organic matter in water must depend, not on its quantity, but its nature. And any comparisons put forward with regard to quantity, irrespective of nature, fell to the ground altogether. Had there been sufficient time, it was his intention to discuss the question of quality as he had the question of quantity ; and he had notes ready for the purpose, but time did not allow of their use. Any general statement, and any conclusion he had formed or expressed, with regard to quality, was formed on a consideration of evidence, and was gone into by him as minutely as he had gone into the question of the influence of quantity. The gist of the whole question in the present state of knowledge seemed to rest on an observation of effects. Of course if you took one week and compared it with another, or one town with another for a short period, you might arrive at almost any result you pleased; but if you took large populations, and examined the statistics for lengthened periods, it would be found that there was absolutely no difference whatever in the health of the population which could be ascribed to the drinking of river water, or spring water ; from which it would seem all these different varieties were, in their different ways, well suited for the supply of large populations.
III.-METHODS OF DISTRIBUTION.
MODES OF GIVING PRESSURE,
WATER DISTRIBUTION AND DUAL
By Col. Sir FRANCIS BOLTON. In former times it was customary to lead water through aqueducts to public fountains, whence it was taken by water carriers to those consumers who could afford to pay for it, while the poorer classes fetched the water from the fountains for themselves ; and this system still exists in certain large cities abroad, such as Constantinople and Venice. In some towns, indeed, even in ancient times, this primitive mode of delivering water was found insufficient for the better class of houses. In luxurious Pompeii, for instance, which was destroyed A.D. 79, a very complete system of distribution appears to have existed by means of pipes, which delivered the water direct to the houses. This mode, however, was by no means general, the inhabitants of most cities contenting themselves, as above mentioned, with the services of water carriers.
A very noticeable want in connection with those towns which derive their water supply from public fountains is that they are, for the most part, without any sewage system, and the evils arising from this serious drawback may be readily imagined, although it is not the object of this paper to describe them. On the other hand, it should be mentioned that the difficulty of carrying large quantities of water in such towns to the houses separately has, from time immemorial, been remedied to a certain extent by the construction of public baths, and other public conveniences for the general health and benefit of the inhabitants.
The mode of distribution which may now be said to be almost universal is by means of cast-iron pipes, and as far as our knowledge goes, in the present state of hydraulic engineering, this system may be considered perfect. Towns are divided into districts, according to position and level, and in each district mains are laid, usually following the course of the principal streets. From these mains service pipes supply all the streets within the area. Each service pipe is provided with a cock at the junction with the main, and a wash-out valve at the other end, fire-plugs
or hydrants being inserted at convenient distances, usually about 100 yards apart. In those districts which are supplied on the intermittent system, the service-pipe cocks are opened and closed at certain intervals; but where the plan of “constant supply” is adopted, they are always left open, except in case of accident, or during repairs.
On reference to Diagram No. I, showing part of distributory mains on this system, it will be seen that the water, on entering the service pipes, enters as it were a cul de sac, where, unless there is a large draught or consumption, it is apt to remain practically stagnant, thus allowing the impurities held in suspension to be deposited on the sides and bottoms of the pipes. It is for this reason a wash-out valve is placed at the end, which, if opened sufficiently often, allows the impurities to be washed out ; but if this precaution is neglected, the impurities accumulate, and when a sudden call is made on the service pipe, find their way to the consumer.
By having no “dead ends," as shown in Diagram No. 2, this difficulty is obviated, as the water is continually circulating in all directions. This arrangement is of great advantage where there is constant supply, as in case of accident at C, the main, B, would supply the service pipes entirely whereas if an accident occurred at A (Diagram No. 1), the whole district beyond would be without water until the repairs were completed. It has the further advantage that should a fire occur at z (Diagram No. 2), both nains, B and C, would supply that and the adjoining hydrants, whereas
Diagram No 2,
a fire occurring at y (Diagram 1), would only have the water passing through the one pipe. Equal facilities occur for washing out the service pipes, if found necessary, by closing the cock and opening the adjoining hydrant.
The pipes should be of iron, of good tough quality, as, if the metal is brittle, difficulty is found in cutting the holes to receive the house service pipes; 2 inch pipes are usually cast in 6 feet lengths, 3 inch to 12 inch, 9 feet length, and 12 inch, and upwards, in 12 feet lengths. In order to ensure uniform thickness, the pipes are generally cast upright, and socket downwards; and to prevent oxidation of the interior, they generally either receive a coating of lime inside, or are dipped whilst hot into a mixture of pitch, oil, and tar, which is usually known, from the name of the inventor, as