are not spoiling a useful process by an unintelligible application of it-one of the great dangers of improvement.

The second point which I have mentioned-the facilitation of contagious or infectious disease by mere proximity-is obvious enough in its generality. Its details belong to Section D.

The atmosphere is probably a much greater carrier of noxious germs than water; but, as Dr. Tyndall has judiciously remarked, the aerial germs appear to be sometimes in a less forward, and sometimes, perhaps, in a more effete, state of development than those which are met with in water, or which have once taken root upon moist tissues. On the average, therefore, resistance to them is probably easier. However this may be, it is clear that we cannot subject the supply of atmospheric air, which is necessary for our lungs and skin, to the same complete chemical or mechanical treatment as we can, and do, when necessary, our supply of drinkingwater. Any attempt at the disinfection of air of doubtful purity must necessarily be of the crudest and most empirical kind. In the present state of our knowledge and resources it can hardly be of interest to the engineer.

The third point affords a remarkable example of what I have just mentioned as the greatest danger of all improvements-their unintelligent use. No one can deny that the watercloset and the sewer are great mechanical improvements; yet they have been great carriers of disease. As applied to the particular problem of getting rid of waste products, especially solid products, I do not think they were any improvement at all on much that we already had. In many towns in Great Britain, where there previously existed a well understood and well carried out scavenging system, I think they have done more in saving trouble than in conducing to health. I think the real key to the problem of getting rid of the nuisance of waste products is to be found in the old aphorism that dirt is simply matter out of place. Hence the first step is to take care that such products shall not become waste; and one condition of this is, that they should not be carelessly mixed. The greater part of the sewage difficulty is, I think, simply the result of neglecting this truth. It is especially the case with London sewage. With our water supply, our watercloset system in houses, our drainage of houses, factories, and streets all together, we have accumulated a river of filth, the complex admixture and enormous mass of which have rendered it most difficult and dangerous to control effectually. I think we shall yet be driven to meet the difficulty at its source in the way suggested-by dealing with it in detail, subdividing both from house to house and from kind to kind, and allowing nothing but the mere washings of the streets to get into our sewers at all. So far as the getting rid of waste products is concerned, I believe we must be content to write off the whole cost of our Metropolitan Main Drainage.

There is another undoubted improvement which the legislature has decided upon applying to London, concerning which I feel no small amount of misgiving lest it should be applied without intelligence; and that is, the constant supply of water in place of the intermittent cistern supply. As a mere mechanical convenience it will be a very great improvement; but I foresee two dangers, one of sewage contamination through the waterclosets, the other the waste of an article already becoming scarce. The first is no idle fear. The experience of Croydon and other places has shown that it is possible to make the water supply and the sewage a circulating system, with fever or cholera as its inevitable consequence. It has been bad enough in several places of moderate size; but in London, whether we regard it with reference to the mass of contaminating material, or to the quantity of human life to be affected by it, the risk has a much more serious aspect. I shall be sorry to see the constant supply established in London without taking some effectual security, either by the interposition of cisterns or otherwise, to prevent the possibility of back draught from the cess to the drinking-water. Without some such precaution, I think the mechanical improvement may be a fatal gift.

I have said that the problem of the crowd, if I may venture so to call that of maintaining purity in the supply of a dense population, is now presenting itself in a new and very difficult form. That is so notably in the matter of water supply; because until now it has generally been possible, by some expenditure in aqueducts and care in the selection of the sources, to obtain a suflicient supply of thoroughly

good water, not always perhaps of chemical purity, but at any rate free from any great contamination of animal and especially of human excreta. This possibility threatens to disappear in the United Kingdom generally; and especially so with regard to the manufacturing districts and to the east of England, not only from the mere increase of the population, but much more from the higher cultivation of the land. The moorlands are everywhere being broken up for the plough; fallowing has given place to heavy manuring and to sewage irrigation, both of which are freely applied to pasture as well as to arable land. The population of bullocks and sheep has also increased with the human population. The result is that the rain is contaminated as soon as it reaches the ground. The surface drainage, instead of being water naturally distilled, flowing off clean grass or moss, is the washings of manure. The spring-water, again, is not pure rain-water which has passed through a rock-filter and has taken up some mineral ingredients, but is simply these manure washings more or less completely filtered. In our streams the water derived from both these sources undergoes fresh exposure and cleansing by aquatic vegetation, but at the same time fresh contamination. The mere statement of the problem in this way carries with it, almost axiomatically, the inference that the effective character of filtration is a matter for quantitative investigation, not for assumption as perfect and complete. We know, moreover, that some of these natural filters have been overtasked.

Let us now turn aside to consider what is the work to be done, and what is, so far as we are able to understand it, the work actually done by filtration.

I believe I am right in saying that with the exception of the strong corrosives, which act like weapons rather than as medicaments, no one really knows what poisoning is. We must take it as an expression used to summarize the unknown and possibly inscrutable chain of events of which we only see the primary cause and the ultimate effect. We may perhaps go one step further in respect of the poisonous effect of organic sewage in its unfiltered form. It contains, for one thing, the dead products of organic decay. A grass filter or an earth filter very rapidly renders this part of the sewage innocuous by oxidizing it. Then it contains germs of animal life, some of which, unless intercepted or killed, prey parasitically on the larger mammalia. Thirdly, it contains vegetable germs, closely allied, it would seem, to the moulds and other small fungi; these, finding a restingplace in our bodies, grow and destroy or spoil the cells of which our own growth consists, much in the same way that the yeast fungus modifies the worts of beer, or that the common mould spoils the flavour of a pot of jam. The effect of such spores upon us is called zymotic disease. The first class of impurities is pretty easily dealt with. Probably the means already exist of calculating at what point any given filter will or will not be overcharged in respect of its defecating function by the oxidation or entanglement of dead matter. But the question of the filtration of living germs is altogether more obscure. We know that many of them are caught and effectually intercepted by both surface and underground filtration; but we do not know in what proportion this intercepting takes place, either on the average of all germs or with reference to each kind of geim which may be present -different questions not always sufficiently distinguished. Then we also know that the life of some germs is destroyed if their development be too lorg retarded. Bateman, Michael Scott, and others afterwards have described the remarkable effect which storing water in dark tanks has in keeping it clear, not only while it remains in darkness, but even under subsequent exposure to light. Now we have at present very little quantitative or well-digested knowledge on these subjects. In fact, little more is known of them than is contained in the crude statement which I have just laid before you. We have no series of experiments to show what or how many germs escape a given process of filtration or storage; and it is not every germ that we need be afraid of: the greater part of them, probably, are quite innocuous. All that the chemists have been able to give us is a dubious estimate of the total quantity of organic matter (whatever that term may mean) which the influent and effluent waters severally contain. They do not and cannot tell us in what form the matter exists, whether dead or alive, animal or fungoid. Now for many purposes the information so given is about as useful as it would be to know that there is animal and vegetable life in a given field, without being told whether

it is corn or couch grass, rats or rabbits. On this subject I think both the engineer and the chemist will but grope in the dark until the biologist comes to their aid, working statistically with his microscope as well as observing particular developments. Whether any observers are yet prepared by preliminary knowledge for such investigations I know not, but sure I am that the need of them has come.

It may be some consolation to the timid or fastidious among my listeners to be assured, first, that only a few organic germs are capable of hurting us; and, secondly, that an overwhelming proportion of the germs of life perishes without reaching maturity or attaining the power of doing mischief. This destruction goes on to an extent little dreamt of except by those who have minutely examined the question. It is not an exaggeration, but in many cases an under-statement, to say that a million germs are produced in most of the lower forms of life for one which ever reaches the reproductive stage in its turn. Numerical evidence is easily obtained of this in the case of ferns and lycopodiums and fungi among plants, and of many worms and fishes and other creatures of lower organization among animals. This constitutes at the same time our safeguard and our danger: a safeguard, by the improbability of our meeting the few survivors of this enormous destruction; a danger, from their rapid increase when they do happen to meet with a resting-place favourable to their development.

What is practically becoming most essential to us just now is to be able to pass from vague generalities, such as these, to definite and quantitative statements.

No doubt much may be done, and is daily being done, to come to the assistance of these natural processes of purification by submitting water of doubtful quality to various operations calculated either to remove certain classes of impurity, or to avoid clogging or otherwise overtasking the natural or other filters. But at present we are working in the dark, and empirically, in fact, applying quack remedies at random, instead of setting to work systematically and intelligently. Much fuller knowledge must be acquired before we can understand our business.

In the meanwhile I think we must view with great and increasing distrust all merely selective sources of water supply, and that, except perhaps in some favoured localities, such as the best of the gathering grounds from which Glasgow is happily supplied, we must not put too implicit confidence in any methods of filtration or boring.

Besides, then, the general investigation which I have just spoken of, there remain two alternatives to consider, each of daily increasing importance in certain localities. One is the separation of the drinking from the ordinary supply; the other is the distillation of the drinking-water. Neither of these are new; and there are many places where they are of obvious necessity, and practised with the greatest care accordingly. I think both require more attention than they have received in this country.

As regards the separation of supply, it surely is not seemly that where there is no scarcity of water, but only a scarcity of wholesome water, the waterclosets and factories and condensers of steam engines should be put in competition with the dry throats of the people for the drinkable supply.

The question of distillation also requires further study. There seems to be no doubt that by subjecting water to sufficient heat we can destroy every living germ in it, and that by distillation we may combine this with the removal of almost all inorganic matter. At present the process seems to be rather expensive, and brings it up to a price which is far too high for its general use. But I think that when the process comes to be carefully gone into, with a view to working it upon a very large scale, it may not be found impossible to effect a considerable saving upon this cost. In fact, the mere necessity of delivering the distilled water at as 1 wa temperature as possible, without the use of too much cooling material, is a security for the employment of as little coal as possible. We should require a settlement with the Excise to prevent the revenue suffering by fraud; but no doubt a compromise could be arrived at if the necessity were felt to be urgent.

The collection and arrangement of my thoughts, with a view to the remarks just addressed to you, has brought before my mind very strongly certain considerations, some of which, being partly of a political character, I shall rather ndicate than discuss.

In the first place, there is an evident and urgent necessity for the whole question of the water supply, at any rate of England, being much more thoroughly investigated and taken in hand than it has hitherto been thought

necessary.

Secondly, there is need for the concentration of the business of the supply and distribution of water (including frequently the management of the gathering grounds), the roads, the lighting, and the drainage in one board for each town or district, preferably the municipal authority. In London, where there is no such concentration, the waste and inconvenience arising from the independence of the road, gas, and water authorities in the mere matter of breaking up the roads is becoming a very serious consideration.

Thirdly, there is a want of knowledge of natural science in the local governing bodies, which is but ill supplied by their employment of professional officers. Much more of it is wanted in the governing councils themselves before their technical advisers can be either properly appreciated or properly controlled. Whether this is to be got by the direct infusion of a professional element into the council itself, or whether it is best to wait for the general spread of natural knowledge, I scarcely care even to form a judgment.

Fourthly, it is a popular delusion, especially prevalent in this Section, that the invention and provision of a mechanical convenience are necessarily an immediate social benefit. There are many cases in which the direct effect is to facilitate personal indolence or carelessness. It is then a positive evil, until, either by natural selection or by experience, more careful habits have been reverted to. There are other cases in which the indirect consequences are more mischievous than the direct advantages are beneficial. Here, again, there is no benefit until those consequences have been met. There is a disadvantage which only attaches to the immediate effects of some particular inventions. On the whole, of course, invention is not only a good thing, but, together with discovery, a necessity of our nature and of our existence. Meanwhile our immediate national necessity is a wider, deeper, more exact, and more general spread of natural knowledge.

On the Removal of Subaqueous Rocks by the Diamond Rock-borer.
By MAJOR BEAUMONT, M.P.

On the Removal of Sand-bars from Harbour-mouths. By M. BERGERON.

Hand-machine for Shaping and Finishing Metal Surfaces. By J. B. BEYNON.

A Flanging-iron and Steel Plates for Boiler purposes. By A. B. BROWN.

On an Engine for Starting and Reversing large Marine Engines.

By A. B. BROWN.

The principal feature of this engine consisted of a combination of steam and hydraulic cylinders, controlled by an automatic valve-gear, which enables the engineer to reverse the largest engines without assistance in a few seconds. This is accomplished by the lever which opens and closes the steam and hydraulic valves being hung partly on the reversing-lever and at its other extreme on the weigh-shaft lever, so that any motion given to it and the valves by the engineer in one direction is counteracted by the movement of the weigh-shaft lever to

which the links of the marine engine are attached. In this way these links follow the motion of the reversing lever, and are locked fast at any degree of expansion in the quadrant.

On a Machine for the Liquefaction of Gases by combined Cold and Pressure. By J. J. COLEMAN, F.C.S.

This paper describes a powerful machine, erected for dealing with 300,000 feet per day of waste gases at the works of Young's Paraffin Light and Mineral Oil Company.

The machine includes

1st. The pumping of the gas by steam-power into a system of tubes externally cooled by water, and from which condensed liquids are withdrawn.

2nd. Employing the condensed gas, after being deprived of liquids, for working a second engine coupled with and parallel to the first, thus recovering a portion of the force originally employed in compression.

3rd. Employing the expanded gas, having had its temperature reduced in the act of doing work, as a cooling agent for a portion of the condensers to near zero Fahrenheit.

On Drainage Outlets through Slob Lands. By A. CRUM-EWING.

The author described the means he had employed to open up a channel two miles long through slob, in the colony of Demerara, for the purpose of reestablishing natural drainage. This slob is a deposit from the great rivers of the northern part of South America; and when it sets in in front of the plantations, completely blocks up their drainage outlets. The method employed was to lay a steel rope all the length of the mud-bank, and, by means of Fowler's clip-drum placed in a small steam-vessel, which had strong drag-harrows attached, to run the whole apparatus rapidly from end to end of the rope. When the water discharged from two very powerful centrifugal pumps was brought to bear after the dredge, a marked effect was produced, and a channel was being rapidly opened deep enough and wide enough to carry off the heavy rainfalls (sometimes as much as six inches in twenty-four hours) without having recourse to pumping-a matter of great consequence, as the expense and risk of pumping are farge.

On recent Attempts at Patent Legislation. By ST. J. VINCENT DAY.

On the Form of Blocks for Testing Cement. By G. F. DEACON.

On the Strength of Concrete as affected by delay between mixing and
placing in situ. By G. F. DEACON.

of 35 acres.

Description of Stobcross Docks. By J. DEAS.

The first portion of ground purchased for the works was in 1845, and consisted At that time a wet dock and tidal basin were proposed, having a total water space of 17 acres and 16 acres of quay space, the length of quayage being 1458 yards. Until within the last few years, however, the Clyde trustees were able to obtain ground on both margins of the river sufficient for the required quay extension, the river itself forming the water space, and requiring little expense to make it available opposite the new quays.

In 1864 the Edinburgh and Glasgow Railway Company (now merged in the North British Railway Company) obtained an act to make a railway from their Helensburgh branch to the authorized docks, with a station immediately on the