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conduits should be avoided, and where it cannot be avoided the two metals should be kept from metallic contact by the interposition of a non-conducting material.

SEWAGE.

I have often thought, and have given public expression to the thought, that, from a sanitary point of view, the production of sewage, ordinarily so-called, that is the water carriage of our house refuse, was a mistake. However, for good or for evil, the plan has been adopted, and we must do the best we can for its satisfactory disposal. The question is a very large and important one, and I cannot treat it in any but a very fragmentary manner here.

The first point I would mention is, that all authorities who have to deal with the disposal of sewage should clearly understand that sewage is a nuisance to be got rid of, and not a thing to make a profit out of.

The next is, that if sewage is to be disposed of to the greatest advantage of the community, the sewage of every place will have to be dealt with on its own merits; no general scheme will do equally well for all.

Many schemes-good, bad and indifferent-have been elaborated for the proper disposal of sewage, but I cannot deal with them here; perhaps we shall hear something about them at this meeting. But with your permission I will throw out some suggestions on the general aspect of the question.

In the first place, I am decidedly of opinion that whatever scheme may be adopted (except destruction of the sewage material by fire), the agents to which the ultimate destruction of sewage is due are living organisms (not necessarily microorganisms), either vegetable or animal. If this be so, our treatment should be such as to avoid the killing of these organisms or even hampering them in their actions, but rather to do everything to favour them in their beneficial work. Now in order to avoid this danger, and at the same time reduce to a minimum the nuisance due to the existence of sewage, we must begin our treatment in the sewers themselves, a step further back than it is usually begun. Of course I am aware that sewers are laid out with a view of bringing the sewage in the shortest possible time from the sources of production to the general outfall; but even in towns of moderate size the time elapsing in the passage of the sewage between these two points is sufficient to render the sewage offensive, at least in summer time, while in large towns the sewage has time to become very highly offensive. No doubt the great bulk of the sewage as a rule reaches the outfall in a short time, but the time which has to elapse before the whole of

the sewage contained in the sewers at a given time is discharged is far longer than is generally supposed. This offence ought to be avoided; how can it be done? It should not be done in a manner to destroy our beneficial organisms, or even seriously to check their action; in other words, the use of disinfectants or of powerful antiseptics should be avoided. I have the less hesitation in saying this, because, on the score of expense, it is practically impossible to really disinfect infectious matter when once it has found its way into the sewers. All that is usually done in this direction is really a deception-no doubt a self-deception -on the part of those employing such means. All we can therefore really do is to deodorise the sewage, and this can be done without in the least interfering with the immediate or subsequent action of the organisms on which we depend for the final destruction of the sewage. The best material for this purpose is, in my opinion, a solution of permanganate of potassium, prepared on the spot from crude manganate by the addition of acids or suitable salts to the same. Sanitarians are, I think, greatly indebted to Mr. Dibdin, of the Metropolitan Board of Works, for bringing, by his energy and courage, the manganates, and consequently also the permanganates, within the reach of practical sanitation. And let it not be supposed that all we effect is simply deodorization of the sewage; but we also in great measure check putrefaction, and thus do away with what seems to be the chief agent in carrying disease germs into our streets and houses, namely, the rising and bursting of gas bubbles from the sewage.

Sewage thus treated will arrive at the outfalls in a practically inodorous condition, or nearly so, according to the amount of manganate used, and is fit for any kind of treatment we wish to adopt, such as:

Sewage farming with untreated sewage.

Sewage farming with sewage clarified by subsidence.
Sewage farming with sewage clarified by precipitation.
Precipitation and filtration.

Precipitation and discharge, if necessary previously deodorised, into a river of sufficient volume to prevent the production of a nuisance. According to the exigencies of each particular locality.

As regards processes of precipitation, I will merely remark that inasmuch as no proportion of chemicals which can practically be employed will do much more than clarify the sewage, the proportion of chemicals employed should be kept as low as is consistent with the object to be obtained, namely, clarification, and that, more particularly, the use of large quantities of lime should be avoided.

To sum up: let natural agencies have their way, assist and direct them into proper channels as far as you can, but interfere with them as little as possible.

Mr. ROGERS FIELD, M.Inst.C.E. (London), moved a vote of thanks to Dr. Dupré for his admirable address. As bearing on the subject matter of that address he might say he had known of more than one case in which water had been analysed by a local chemist and pronounced to be good, when he himself had been nearly certain from the surroundings that it had been polluted with sewage. The discrepancy had been cleared up for him by Dr. Dupré. The opinion that the water was unpolluted was given simply on the general grounds that water which contained only such and such ingredients was unpolluted. But directly a sample of unpolluted water of the district was obtained and compared with the water in question it was found that the water was clearly polluted.

Mr. J. B. GASS (Bolton) seconded the vote of thanks to Dr. Dupré for his admirable address, and remarked on the vital importance of correct and high standards for the purity of water for domestic purposes, as a question, the application of which directly affected the health of the whole population.

Dr. A. DUPRÉ, F.R.S. (London), expressed his thanks for the compliment, and then called on Mr. Frankland and Dr. Parkes to read their papers, saying it would be better to discuss them both together.

On "The Application of Bacteriology to questions relating to Water Supply," by PERCY F. FRANKLAND, Ph.D., B.Sc. Lond., F.C.S., F.I.C., Associate of the Royal School of

Mines.

ALTHOUGH the modern development of the study of bacteria and other allied micro-organisms has now attracted the attention of the public for a number of years, and has excited such general interest that references to "bacteria," "germs," "microbes," and the like are frequently to be found in the daily papers and other prints freely circulated amongst all classes of the population, yet it is often only too palpable from these very allusions that but little sound knowledge concerning these microorganisms has penetrated beyond a comparatively limited circle.

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I am, therefore, of opinion that on the present occasion it will not be out of place to point out briefly some of the more important applications of bacteriology to the subject of water supply.

In the first place it may be stated generally that bacteriological science has so far been applied to the investigation of the sanitary aspects of water supply in three different ways:1. In the actual detection of disease-producing or pathogenic micro-organisms in potable water.

2. In determining the influence which filtration and other methods of water purification (both natural and artificial) have on micro-organisms in general.

3. In ascertaining the fate of disease-producing or pathogenic microbes when introduced into different kinds

of water.

We will deal with these three applications of bacteriology in order:

1. The detection of pathogenic micro-organisms in drinking

water.

It is frequently and very generally supposed that the allimportant task of bacteriology in connection with drinking water is to ascertain whether or not a given sample of water contains micro-organisms capable of producing disease. Now, even assuming that we were fully acquainted with all the microorganisms capable of producing disease, which we certainly are not, even then the examination of water for hurtful microbes would be a comparatively unimportant application of bacteriology, one possessed of only limited and local interest, and if relied upon alone, capable of leading to most erroneous and dangerous deductions. For instance, of what value would it be to ascertain that a sample of some particular water supply was free from the infectious principle of typhoid fever or cholera on some particular occasion? Information of this kind has obviously next to no interest whatever, for the absence of these infectious principles on one occasion affords no indication that they may not be present at a future time. Imagine the absurdity of examining all the potable waters of England for the specific poison of typhoid fever, and assuming that the poison, if present, could be detected with unerring certainty, how many of the most dangerous waters would escape condemnation because at any particular moment the chance of their containing the poison is infinitesimally small!

It cannot be sufficiently emphasized that the mere detection of zymotic poisons in water is a matter of complete unimportance from a general point of view, and the fact that the detection of

even the few known zymotic poisons is at present a matter of the greatest difficulty, and in consequence of the almost invariable and enormous preponderance of harmless organisms, is really of but little consequence, as the important bearings of bacteriology on water supply lie in an altogether different direction.

It should, however, be mentioned here that the organism which is widely credited with being the producer of cholera was by Koch found during an epidemic in the tank-water used for drinking in India, and quite recently the organism, which is believed to be the contagium vivum of typhoid fever, is alleged to have been found in a well-water which had been used by persons suffering from this disease.

It is obvious that this first application of bacteriology to water-sanitation is of far more interest in throwing light upon the manner in which particular diseases may be disseminated than in forming our opinion as to the fitness of water for domestic use. It is in fact of interest rather to the student of disease than to the student of water-sanitation.

2. Determination of the Influence which Filtration and other methods of water-purification (both natural and artificial) have on micro-organisms in general.

Inasmuch as a large proportion of all the water available for domestic use has at some period of its history been exposed to the risk of contamination with infectious matters, it obviously becomes a matter of primary importance to ascertain with what degree of probability these infectious matters, should they have gained access to the water, would be removed in the subsequent natural or artificial treatment which the water has undergone.

Now the infectious matters which the systematic investigation of zymotic disease has revealed are in every case micro-organisms, and thus the study of the removal of infectious matters from water becomes synonymous with the study of the removal of micro-organisms from water. But as we are acquainted with only a few of these infective micro-organisms, it is necessary to study the influence of methods of water-purification on microorganisms in general, irrespective of their hurtful or harmless character. On this subject, bacteriology in its present stage of development is capable of throwing the most important light.

In a paper which I had the honour of bringing before the last meeting of the Sanitary Congress at York, I had occasion to point out some of the results which I had obtained in the application of bacteriological_methods to the examination of the London water supply. I there showed how the process of sand-filtration, which is employed by seven out of the eight companies supplying the metropolis, is in reality an operation

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