provements set on foot as a result of that epidemic have revolutionized the city, and will have resulted in the saving of many thousands of lives every year; for the principal effect of efforts to guard against cholera is to abolish, or greatly diminish, mortality from various other causes. That epidemic at Naples led, further, to the enactment of a new sanitary code for the Italian kingdom, and to many excellent improvements in other Italian cities and towns besides Naples.

Far more widespread throughout Europe, however, will have been the improved sanitary arrangements resulting from the cholera invasion of 1892-93. It is in Germany, doubtless, that the most important effects will appear. The German cities have not, until lately, been largely impelled by the sanitary motive, in their municipal activities. They have done wonderful things, and have shown a splendid capacity and business thrift. But while the public health has been the dominant motive in the development of the municipal functions of some of the British cities, good financial results have seemed to be the chief criterion of success in German municipal government. The broad generalization is too sweeping, yet it is upon the whole a safe one. While taking the lead of all nations in the scientific study of the problems of the public health, the Germans have not been the most eager people in the world to spend millions of money in the application of hygienic principles. Fortunately for them, they have the best scientific leadership that any country can afford, and at the same time they have by far the best administrative mechanism. All that had been needed, therefore, was the motive strong enough to open wide the public purse - strings. The cholera appears now to have supplied it. All over Germany the learned doctors and bacteriologists are dictating terms to the awakened municipal authorities.

The most interesting centre of this new sanitary activity is stricken Hamburg. There is very much in its conditions and in its plans and undertakings that ought to interest the intelligent people and the officials of our American cities. Let it be said in preface that Hamburg was most unjustly treated by the major part of our press during the summer and autumn of 1892, and that most Americans have an entirely erroneous impression of it. Until late years it has received comparatively few American visitors; and of course for two seasons it has been shunned. Even the travelers who patronize the fine steamers of the Hamburg-American Company hurry on to Berlin, and learn nothing of this noble old Free Hansa city and magnificent port. In America it is chiefly known as the place from which so many undesirable emigrants take shipping, and has the reputation of being indescribably filthy, overcrowded, ugly, and uninteresting, a place, in short, to be avoided. No impression could be further from the truth. The emigrants go from Hamburg for the same reason that they land at New York: the one, like the other, is without rival as the greatest port of its continent. Ships go everywhere from Hamburg. Its dock and harbor arrangements excite the enthusiastic admiration of every visitor. There is no such sight elsewhere in the world. The boasted Liverpool arrangements are far inferior. Within a decade there has been expended by the German Empire and the city of Hamburg a sum approaching forty million dollars in the construction of this vast shipping terminal, the modern conveniences of which make everything along the New York docks seem absurdly effete and obsolete.

Hamburg is an infinitely more attractive and picturesque city than Berlin. The dull and somewhat cheap monotony of the huge new imperial capital is al most painful after a few days of Hamburg's variety and charm. The city's

architecture combines the modern with the medieval in the most delightfully unexpected ways. Many whole streets of the high-gabled, timber-framed, quaint-windowed houses of the old sixteenth and seventeenth century Hanseatic merchants remain in good condition; and yet the city as a whole is distinctly modern in its architecture. Far from being hopelessly congested and void of breathing-spaces, there are a number of tree-lined thoroughfares, much broader than are to be found in leading American cities, and in the very heart of the city there are large water spaces and park areas, with extensive girdling promenades, and every facility for healthful outdoor recreation.

A dignified and splendid city is Hamburg, with its 600,000 inhabitants, its immense commerce with all parts of the world, its unusually intelligent merchant body, its suburbs of handsome villas, its modern growth and enterprise, and its fine traditions and history that bind it to a noble past. And its very life has been the great river Elbe. But the Elbe, which has been its commercial mainstay, has brought death as well as life. The river has always supplied the city with water for drinking and domestic uses, and its unwholesomeness has long been fully confessed. But many things have prevented, until recently, the firm attempt to solve the paramount sanitary problem of the city's drinkingwater. Early in the seventies an elaborate investigation resulted in a report advising the filtration of the entire Elbe supply. But opposition arose, the discussion was protracted, and nothing was done. The inclusion of Hamburg in the new German Empire, and its accession at last to the German customs - union, led to the concentration of the municipal energy upon the development of the port facilities. The abandonment of Hamburg's status as an independent port, and its inclusion in the tariff system of Germany, took practical effect in 1888, and the in

fluence upon the city's traffic and growth was both immediate and very important. Meanwhile, the scientific consideration of the water supply had not been altogether suspended, and the city's enhanced importance furnished a new reason for action.

In 1890, it was actually determined to proceed at once with the construction of an extensive plant for the filtration of a supply of Elbe water equal to the entire demand upon the water system for all purposes. Expert investigations, with reinvestigations and all sorts of crossexaminations, had resulted in a plan that was adopted with confidence. It was pronounced feasible by the municipal engineers to have the filtration plant ready for use in 1894. The cholera emergency led to prodigious efforts, and the new system was put into operation in May, 1893, nearly a year ahead of time.

The last seventy-five miles of the Elbe form an estuary of the North Sea, and the tidal movement up as far as Hamburg is considerable, amounting to several feet on the seaward side of the city. The Elbe flows northward; and the old waterworks were situated on the southern edge of the city, the intention being that the water should be pumped from a point in the stream that lay above the brackish and polluting influences of the flood tide. The "intake" was in the middle of the river, just opposite the large pumping station, high water tower, and adjoining reservoirs which constituted the old waterworks that served the whole city. As a matter of fact, the intake was not far enough upstream to escape serious contamination from the recession, at flood tide, of the polluted water of the harbor and lower stream. One must remember that the Elbe carries off the entire sewage of Hamburg; and that the stupendous aggregation of ships, of wharfs and warehouses, and of manufacturing establishments makes the water of the port about as filthy as possible. The sewer system of Hamburg is

by no means a bad one. The houses are all connected with well-built street mains, which empty into several large collecteurs, or sewage canals. These principal conduits in turn converge and join in one huge discharging sewer tunnel, which is carried well out into the channel of the river, and empties at the lower edge of the city. The discharge is dammed in and held back during the hours of inflowing tide, so that the main harbor, and the numerous branching navigable Fleete, or canals, that make Hamburg something like Venice, may not be fouled and gradually filled up by subsidence from the immense volume of liquid filth. The sewer gates are opened only when the ebbing of the tide joins with the ordinary flow of the river to give a sweeping current out to sea. This, at least, is a far better arrangement for sewage disposal than certain American cities lying on tidal water possess, which dispense with collecteurs entirely, and discharge their sewage at numerous points all along the river frontage.

But it is far from being a perfect system.

For although the Elbe estuary is a broad stream, the cities of Hamburg and Altona have become so great that the combined volume of their refuse material is enormous; and the plan of discharging at ebb tide alone cannot wholly prevent the subsequent backflow of pollution from the sewers.

Quite apart from any and all local sources of contamination at Hamburg, the Elbe water is by no means pure, for the river drains a populous valley, and has many large towns and villages on its banks. Hamburg ought long ago to have extended its intake far enough upstream to make perfectly sure that its citizens would not receive again through their water-pipes the fouled effluent of their drains. But at the time of the cholera visitation of 1892 the old intake was still in use, and was undoubtedly within the sphere, at flood tide, of harbor refuse and city sewage. An essential fea

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ture of the new water system, therefore, has been the extension of the receiving tunnel up the river to a point some miles above the now abandoned intake. work involved very large expenditure, since the new tunnel had to be constructed under the bottom of the river.

The filtration system, however, is the interesting feature of the new Hamburg water supply. It is by far the largest and most successful "plant " for the removal of impurities from drinking-water that any city has yet instituted. It happens that Hamburg is so situated that it is practically compelled to draw its water supply from the river. There are no mountain sources accessible. Naples, like Vienna and Munich and Glasgow, has been able to secure abundant water from high and uncontaminated mountain regions. But Hamburg lies in the lowlands, at the mouth of a broad valley. We have a number of cities in the United States that seem to be under the necessity for all time of drawing their water supplies from the much-polluted rivers on the banks of which they are situated. For these cities the question of an effective method of filtration has the very highest consequence. From Minneapolis to New Orleans the cities of the Mississippi Valley are concerned. Cincinnati, Indianapolis, Louisville, Omaha, Sioux City, Kansas City, and many other cities must continue to drink river water. If the Elbe and the Rhine can be completely filtered, there will be no question about American rivers.

A general description of the Hamburg system can easily be given. The city was fortunate in owning two large islands in the Elbe, which have been connected by a narrow embankment, and which extend from a point near the old waterworks upstream for a distance of about two miles. The uppermost of these islands, the Billwärder Insel, is the larger of the two. Somewhat further up the river is the new intake, with its well screened and guarded opening. The re

ceiving tunnel is perhaps ten feet in diameter. On this upper island have been constructed four large reservoirs, or sedimentary basins, as it might be better to call them, each of which has a capacity approximately equal to the supply of the city for one day. A new pumping plant on the island lifts the water into these basins. The four are used in rotation. It has been found by experiment that the best results are attained by allowing the water to stand undisturbed for about twenty-one hours. Sluices and valves enable the basins to be used separately and successively. Thus, while Basin I is engaged in feeding the filters that supply the city, Basin II is full and closed for a day's deposit of sediment, Basin III is being pumped full from the intake, and Basin IV, which is quite empty, is in process of being scraped and cleansed. When Basin I's supply has been drawn off, it in turn is closed for removal of sediment, Basin II is put into connection with the filters, Basin III is full and closed, and Basin IV, having been cleaned out, is again in receipt of a supply from the river. And so the rotation is complete. Each of these sedimentary basins has a superficial area of perhaps twenty-five

acres.

The screens at the intake mouth of course keep out all large extraneous objects. The settling process in the great basins further disposes of fine sand, and of very much of the mud and silt that discolor the water as originally received. But from the hygienic point of view, it is obvious that nothing of very radical importance has been gained by the mere fact of a day's rest in a settling basin. It is in the filtering basins that the revolutionizing results are attained.

The lower island, the Kalte Hofe, lying just above the old waterworks on the east bank of the Elbe, at the Rothenburg suburb, presents a sight best seen from the top of the waterworks tower, and one quite worth the climb of 365

steps. One looks down upon an island perhaps three fourths of a mile long and one fourth of a mile wide, the greater part of which is covered with even rows of rectangular basins, each of which has a surface of 7500 square metres, or about two acres. There are twenty-two of these open filter basins. To describe their mechanism in detail would be to attempt an engineering article. It will be enough to tell in a general way how they are made and how they work. In principle they are not original. Sand filtration has been in use to some extent for many years. Altona, the flourishing manufacturing city of 150,000 inhabitants that lies solidly against Hamburg on the side towards the sea, and is virtually part and parcel of the larger city, has for thirty years used sand filtration to make Elbe water potable. Berlin also filters through sand-lined basins a considerable part of its drinking-water. The London water companies have made successful use of the same system, and other cities have had some experience of this mode of water purification. The Hamburg plant on the Kalte Hofe is notable, therefore, not for the introduction of a new principle, but rather for the utilization of an old principle in a far more complete and successful working plant than any other city has yet established.

The filter basins on the Kalte Hofe, like the large sedimentary basins on the Billwärder Insel, are constructed with the utmost care, being lined very solidly with clay, concrete, hard brick masonry, and cement plaster. Across the floor of each filter basin are many large pipes perforated with countless holes. The basin itself being ready and the punctured pipes being in place, the process of filling begins. First comes a layer of small, well-selected stones, covering the floor to a depth of about eight inches. Then is spread, to a like depth, a layer of gravel; that is, of stones smaller than those forming the bottom stratum, but much coarser than the layer of coarse

sand, also eight inches deep, that is next placed above it. Upon these three foundation layers is deposited the principal material of the filter, namely, a layer of fine sand, one metre (nearly forty inches) deep. When the filter is in use, the water stands exactly one metre deep on the metre of fine sand. Ingenious automatic regulators so control the inflow and outflow as to keep the water at an unvarying depth of one metre. It would be superfluous to attempt a detailed explanation of the admirable adjustment of all the parts of the water system to one another. It is enough to say that the pumping facilities are well adapted to the requirements of the sedimentary basins, that the filter basins are nicely adjusted to receive and dispose of the quantity discharged from the Billwärder Insel, and that the arrangements of the old water station on the mainland at the Rothenburgsort are fully equal to the reception of the purified effluent of the filters, and its distribution throughout the entire city.

It must not be supposed that this system, when once established, needs no further care or attention. The filters are all under constant inspection, and one by one they are cut off temporarily from active service in order to be emptied into the river and cleansed. Adjacent to the group of filter basins is an establishment fitted up with facilities for cleansing the sand and small stones. Ordinarily, it is found quite sufficient to remove a few inches of the fine sand for purification, leaving the rest of the filter undisturbed. It is not, indeed, desirable to take away all the deposits that the sand retains from the water as it trickles through. A certain amount of "scum" must be collected before the filter is at its best. It must be remembered that the chief purpose of the filter is the removal of microbes, whose existence can be ascertained only by bacteriological tests. These bacilli are so small that some millions of them would not feel

crowded on the point of the finest nee dle. A yard or two of ordinary sand and gravel could therefore hardly be expected to filter out the microbes as if they were so many crawfishes. The experts tell us that it is the scum, collecting on the sand and filling the interstices between the stony particles, that somehow manages to detain the microbes, while the water passes on purified and wholesome.

Let no one suppose that this is a mere matter of conjecture, or of an occasional test with dubious results. The effect of the Hamburg filtration upon the bacteriological condition of the Elbe water is now a subject of constant examination and precise knowledge. The whole system has, during and since the summer of 1893, been operated with reference to the fact that the Elbe has been discovered to contain cholera germs, and that Hamburg proposes to give its people a water free from those germs. To this end, the director of the city's hygienic laboratory has been accorded an almost dictatorial authority. At the time of the epidemic in 1892, the distinguished authority Professor Geffke, of the University of Giessen, came to Hamburg to assume temporary charge of sanitary arrangements. He brought with him from Giessen, as his assistant, and left behind him in control of the Hygienic Institute, a young and rising bacteriologist, Professor Dunbar. Dr. Dunbar very rapidly and effectively developed the Hamburg municipal laboratory into one of the most important in the world, and gave it a practical relationship to health conditions that the authorities of Hamburg could not fail to recognize. Dr. Koch came later from Berlin, on behalf of the imperial government, to aid and advise in the struggle to subdue the epidemic, and he was surprised and delighted to discover the rare scientific quality and the comprehensive scope of the work Dr. Dunbar had already accomplished. Dr. Koch thereupon acquiesced very heartily in