ORIGINAL PAPERS.

ON THE PROBABILITY OF AN INVASION OF CHOLERA IN EUROPE.* By Privy Councillor Dr. MAX VON PETTENKOFER.† SINCE cholera has begun to show its Medusa-like head in some of the Egyptian towns, the danger of its spread to Europe has become apparent. Nothing is more natural than that the different States of Europe should ask themselves what can be done for the protection of their populations. For Munich this year the cholera question is one of the highest importance in connection with the International Art Exhibition, which is attracting visitors from all parts

of the world. But even if cholera should find a footing this summer or autumn on the coasts of the Mediterranean or Black Seas, it will hardly find its way to Munich.

Álthough the origin of cholera is still very obscure in some points, investigation has nevertheless established certain fundamental facts that do not admit of doubt. Cholera in its epidemic form does not depend solely upon a disease poison (or, as we may say, upon a yet undiscovered cholera organism), which is conveyed through human intercourse, but also upon the receptiveness of the locality to which this cholera germ is brought. There are places, and even large cities, which have always successfully withstood the epidemic influence of cholera, even although individual cases have been from time to time introduced. We may cite as examples in our own near neighbourhood the cities of Stuttgardt, Salzburg, Innsbruck, &c.; and in France, Lyons and Versailles. Such places are said to enjoy immunity from cholera. But even places which do not enjoy complete immunity may do so at certain times; that is, they are not always victims of a cholera invasion when such invasion is possible. Munich, for example, has suffered only three times from cholera since the disease became known in Europe-viz., in 1836–7, 1854, and 1873-4-whereas Berlin has suffered on every occasion. There is also not only a local but a seasonal susceptibility for cholera as well.

In its permanent home in India the disease does not act differently, for there more than a thousand years' experience has shown that it has its seat not in men themselves or in any particular class, but in particular localities of India, in Lower Bengal, from which it spreads only occasionally through the rest of India, and only to such places as are proper for its propagation, by reason of the indispensable susceptibility of locality or season. Even the per

manent or endemic seats of the disease are not at all times equally dangerous; for instance, in Calcutta itself there may be one year only a couple of hundred cases, whilst in another they may be counted by thousands. Even the seasons of the year show very marked differences, so that on the average the greatest number of cases occur in the hot and dry period (March and April), and the fewest during the hot and wet season (July and August).

That human intercourse must have a strong influence upon the spread of the cholera germs from

From Neueste Nachrichten und Münchener Anzeiger, July 14, 15, and 17, 1883.

For this summary of Professor Pettenkofer's important and interesting paper we are indebted to the kindness of Professor de Chau. mont, F.R.S.

cholera localities is self-evident: the endemic cholera of India began to spread to other countries as soon as intercourse became more rapid by the increase in the rapidity of the means of transit (the first steamer made its appearance in Indian waters in 1823): before we had communication with India we had no cholera. But it is a grave error, as is proved by the recent observations in India (Reports of the Sanitary Commissioner, Dr. Cuningham, from 1868 to 1881'), to assume that those sick of cholera form the only, or even the chief, starting points in the Attendants upon cholera spread of the disease. patients are usually remarkably free from it. Cholera cholera patients. infection starts from a cholera locality and not from

As an argument against the correctness of this view, outbreaks of cholera on board ship are someclosely the occurrence of cholera on board ship, we times cited, but, so soon as we investigate more must be convinced that ships are in the category of localities which, as a rule, enjoy immunity from the disease. It is a rule among seamen, grounded on long experience, that if cholera cases break out intercourse with the shore should be immediately among the crew of a ship lying in an infected port, broken off, and that the ship should sail for the open sea with both sick and well on board, under which circumstances the disease, as a rule, rapidly ceases. Sickness of longer duration, or epidemic outbreaks on the high seas, are rare and isolated phenomena; but when they do take place they make a great noise and are reported in all the papers. But people forget to ask how many other ships have left the same port and sailed the same course, and how many cases they had. When this question is put and answered, we have generally reason to be surprised at the immunity that ships at sea enjoy. For example, the lines of steamers between Calcutta and Mauritius and between Europe and New York have been carefully inquired into. An example from the latter may be here given. According to the lists of the Emigration and Harbour Board of New York, there travelled in 1873 on board ships which carried emigrants not less than 316,956 persons in 760 voyages from different parts of the world, of whom 266,055 came from Europe; and of these 113,920 came from England, and 152,135 from the rest of Europe. As England was free from cholera in that year, we shall reckon only the 152,135 from the Continent as coming from cholera localities. What, then, was the number of cholera cases ascertained to have occurred on board about 400 ships, carrying districts in Europe? Cholera occurred on board 152,135 persons to America from cholera-tainted only four ships in all, the total number of cases being 100.

and landed at New York on September 10, with 1. A ship sailed from Hamburg on August 27, nine cholera cases on board, of whom two died in quarantine; and there were besides two deaths on the voyage, the bodies being thrown overboard. All the eleven cases belonged to two German families, who appear to have gone on board with the disease among them. Among the other passengers, more than 300, there was not a single case.

2. A steamer sailed from Havre on September 12, and on the 16th lost a man, whose body was thrown overboard. She reached New York on the 24th of the month without any other cases occurring.

3. On October 6 a steamer left Stettin with 298 passengers. On October 21 she had three fatal

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cases of cholera; on the 26th she arrived at New York without any more fatal cases.

4. A steamer left London on the 18th and Havre on September 20, and on October 18 she had a fatal case of cholera, and the body was thrown overboard. She arrived at New York on October 28 without any further case. Thus, out of 152,135 passengers eight deaths took place, equal to 0.0052 per cent., and it would not make much difference if, in 1873, out of the 400 ships several had had cholera outbreaks, as actually happened before, for instance, in the Virginia, the England, the Franklin, &c. If cholera cases on board ships which have sailed from a cholera-stricken port remain as a rule isolated and incapable of spreading infection in their thicklypopulated surrounding, so also, in cases where an outbreak on board is so severe as to necessitate the return of the vessel after setting out (Leibnitz), we are unable to accept the sick as a source of infection, but must look for it elsewhere. In those cases the origin of the outbreak is undoubtedly from the shore-from the lodging-houses' in the case of emigrant ships, and from the barracks in the case of transports and men-of-war. For instance, six companies from different garrisons were embarked on board an English steam transport, three from a barrack and three from a camp. Several days after sailing cholera broke out, and many fell victims to it. It came out that every case had occurred among the three companies from camp, and that not one had shown itself among those from the barracks or among the ship's company. In the Indian transports it has been frequently observed that the disease has broken out among the crews, whilst the soldiers have remained free from disease, or vice versa; everything depending upon where the men started from. They must either have embarked already infected or have brought with them a certain quantity of infective material in some shape or other. Ships transport immature cholera germs from cholera localities, but in order that the germ may multiply and become infectious it must be first again brought to land, when its power depends upon the fitness of place and season already referred to. If the germ is a much longer time in being brought to land (on account of the length of the voyage, for instance) it generally dies out; hence, in spite of the enormous amount of intercourse by sea between England and India, cholera has never been thus introduced direct into England, nor even into the Cape of Good Hope or Australia, which have never suffered from cholera. England has always received it through the continent of Europe.*

THE SPREAD OF CHOLERA.

However certain the influence of human intercourse upon the spread of cholera may be proved to be, we must nevertheless be careful not to overestimate it, or to look upon it as the only necessary condition.

When the means of communication in India itself became greatly increased by the establishment and development of railways, it was thought that a very considerable change in the rate and direction of spread of cholera would be observable; but as it has turned out the new conditions have not produced any material change. The same thing has been observed among ourselves in Europe. In Germany,

* Except in 1866 when it appeared to reach Southampton by sea from Gibraltar. (Translator).

for instance, there is no country so thickly populated and so cut up by railways as Saxony. Since 1836 cholera has appeared there in eleven different years, but-according to the official reports of Günther and Reinhard-its spread has not been in any way influenced by the lines of railway. The same places were always the sites of cholera, whilst others remained protected in spite of the railways. In Saxony it was also shown that the epidemic development of cholera took place only at certain times. Every year of severe epidemic was preceded by one of slighter invasion. Thus, in 1849 there died 488, and in 1850, 1551; in 1865, 358, and in 1866, 6,731; in 1872, 4, and in 1873, 365.

That the cholera germ need not necessarily become active at once, when it is sown in a locality, we had good occasion to see in the visitation at Munich itself in 1873, when the epidemic was divided into two parts, a summer and a winter outbreak. Munich lies on three terraces on the left bank of the Isar. The summer outbreak was almost entirely limited to the two higher terraces, whilst in the lowest there were at most a few sporadic cases. The summer outbreak, like that of 1854, showed itself in the beginning of August with a few cases, but it disappeared entirely towards the end of October, to reappear again with greater severity in November, when the district which suffered most was the lowest lying terrace which the winter outbreak had spared. If, however, we admit, as indeed we must, that the disease arose from intercourse between Vienna and Munich, then the cholera germ must have been introduced from the upper to the lowest terrace in August, and from the Turkish barracks to the Isar barracks, where the disease appeared for the first time in November, after a lapse of three months.

These facts, which are incontestable, are too little regarded in this time of possible cholera invasion, both by the public and by the authorities, who seem to think that the only possible prophylactic measure is, either to arrest the cholera poison in its way hither or to destroy it by disinfection. We cannot deny that such steps would be effectual against cholera if it were possible to carry them out, but are we prepared to prohibit all intercourse with everything and everybody that might bring the cholera germ? Most people believe that it is only the sick, and what may have touched them or been in their neighbourhood, that are capable of conveying the germ, but that is an error. The quarantines and military cordons again proposed at the present time can only take the sick as the starting and closing points, and they will no more succeed in arresting the disease than the quarantines and cordons of the year 1830, with which cholera was received on its first appearance in Europe in the present century. On account of their uselessness and their cost they were given up, but people are still quite prepared to begin with them again. Efforts are being made especially in France in that direction, but however details may be altered or new disinfectants be used, it is exceedingly doubtful if any better success will attend them than before. It may indeed be said that by means of quarantines and cordons, if they are sufficiently multiplied, a certain amount of cholera poison will be arrested and destroyed; that, in short, their effect will be much the same as a good preventive service against smuggling-for even, if it does not entirely prevent smuggling, it certainly

The name of barracks in Munich, built in former days by Turkish prisoners. (Translator.)

limits it very considerably. It must not be forgotten, however, that there is a vast difference between articles of merchandise and cholera germs. If a single ox, for instance, is smuggled in, it remains a single ox, and does not immediately develop into a whole herd on the other side of the boundary line. But if a single bacterium gets through in an appropriate medium for its nourishment, it has the power to increase million and billion-fold in the shortest space of time. If a smuggled ox or a smuggled bale of merchandise could immediately increase into a herd or into a warehouse so soon as they passed the revenue boundary, then the preventive service would never have been established, or would long ago have been recognised as useless.

We can imagine no better quarantine than that which was established at Malta against the cholera in 1865. That small island, so favourably situated for guarding against all intercourse from without, hoped to be successful in preventing the entrance of cholera. From the moment that cholera was telegraphed from Alexandria, every vessel from Egypt was put in quarantine in a small island (Fort Manoel) in the harbour. None of the Maltese who had intercourse with the ships that arrived-such as men who helped to coal the vessels-were allowed to return to their homes, but were obliged to remain in the lazzaretto. But in a few days cholera broke out in various places throughout the island, just as it had done before, no more and no less, although those places had had no intercourse with the quarantined ships, people, or goods. Quarantines and cordons, to be useful, ought to be in constant operation, just as cholera is constant in India, from which it can be introduced every year. If we could by stringent regulations reduce or delay intercourse with India until it was diminished to the rates of communication of the last century, then cholera would no longer reach Europe. But in order to break through such cordons we should have bloody wars, which would cost more lives than those lost by cholera-lives, too, of the most valuable and productive ages, whereas cholera chiefly carries off the weak. If we begin with those stringent regulations only when cholera declares itself in Egypt or in Russia, then shall we always be too late. The same intercourse which in 1865 had brought the cholera poison to Alexandria, had also already brought it to Malta before any epidemic broke out in Alexandria, and in Malta it developed itself a few weeks later, but in any case earlier than the arrival of any cholera cases from Alexandria itself. This year it is the same as in 1865. The English have now proved that the cholera in Damietta could under no circumstances have arisen from cholera cases introduced with the Indian troops, and in that they are right; but they are wrong in their inference therefrom, viz., that the cholera was not brought from India, but arose spontaneously in Egypt itself. The cholera germ could perfectly easily have been introduced in the previous autumn or winter, without causing cases of sickness; and it no doubt found this year for the first time at Damietta the suitable soil and other conditions for developing its infectious force. That cholera germs may lie dormant for a long time in a locality, and then develop to infective activity after many months, is proved not only by the periodic march of epidemics in the endemic districts of India, but also out of India, too. The disease has often been observed to lie by during the winter in

Russia or in East Prussia. Pistor, who has carefully followed the course of the cholera in the district of Oppeln from 1831 to 1874, points out that already in 1831 the disease continued till the beginning of winter and then stopped entirely, to reappear again in 1832, in July, August, or September, without any fresh importations being proved. If cholera germs can lie so long dormant after having given signs of life, so must we admit they can lie dormant a considerable time before giving visible signs of life at all. This explains, also, cases of explosion of local epidemics without any recent importations being proved, as well as cases where the introduction of the disease and the outbreak seem to be almost simultaneous. In Egypt cholera has usually begun in June or July, and neither there nor in Malta has it shown itself in winter. Compared with 1865, the cholera this year in Egypt is good two weeks later. Sometimes the cholera localities in Egypt and the Mediterranean are in a favourable condition for its development as regards season, and they will have cholera in spite of all quarantine; but if they are not in this condition they

will remain free even if cholera cases should be actually introduced.

THE PREVENTION OF CHOLERA.

Most men, and many physicians, think still that if quarantine and stringent regulations, disinfection and isolation of the sick are useless, then nothing can be done against the spread of cholera; but when the danger is obviously threatening we cannot remain quiet with our hands in our pockets. People can still do much in the contagionist direction, and even quiet the minds of a good many people, but all efforts in this direction will be of no avail. From our standpoint of localistic influence we must turn in another direction for rules and adopt another kind of activity, which will, indeed, be just as ineffectual as quarantine in stopping the spread of the cholera poison, but which will operate upon the topical and seasonal tendency to disease in our places of habitation, and assist in converting, not indeed at once, but gradually, our soil susceptible to disease into one which will enjoy immunity therefrom. For this we must have cleanliness in person, house, yard, and street, especially by means of careful and regular removal of all foul waters from our dwelling-places, which waters are at the present time so constantly sent direct from our dwelling-houses into the soil we dwell upon, there to form appropriate nourishment for lower forms of life. That the seasonal tendency to cholera has something to do with the water in the soil, and particularly with its fluctuations, has been distinctly shown in the three epidemics at Munich, as well as in its own endemic home. Cholera in Munich has always occurred after a high ground-water level in the driest months, and in Calcutta on an average of thirty years the cases in the wettest month, namely, August, towards the end of the rainy season, have been seven times less than those of the driest month, April. A good waterservice, efficient drainage, and the abolition of all cess-pits (or dead-wells), even those for the reception of rain-water, are prime necessities. Thoroughly good drainage, by immediate removal of all dirty water, deprives all organic life in the house or soil of nourishment for any lower organisms, to which class the cholera germ certainly belongs. Impure soil soon purifies itself, if man will only cease pour

ing fresh impurities into it. In a pure soil the ground-water may fluctuate as it pleases without doing any harm. In measures such as these lies our best protection against cholera and all other diseases which have anything to do with the soil.

Examples of this of a striking character are already known. In England, by the advice of Mr. Simon, the advent of the severe outbreaks of cholera in 1848 and 1854 was met, not by quarantine, but by the most strenuous endeavours to improve the water-supply and drainage all over the country. The result was that, although cholera reached England in 1865, it passed but lightly over it, and in 1872-74 there was not a single case, in spite of the most constant communication with the infected Continent. The city of Dantzig had always been until recently a true cholera nest, whenever the disease came into its neighbourhood. In the beginning of 1870, under the energetic management of its mayor, von Winter, the new water-supply and drainage system after the English model was completed. In 1873 cholera attacked the suburbs (Neufahrwasser, Henbude) with its usual severity, but this time the city itself escaped with 160 cases, whereas previously they had been counted by thousands.

We in Munich are, I think, entitled to regard the further development of cholera in Egypt, and even, it may be, in Southern Europe, with equanimity, and that on several grounds. The history of cholera teaches us that it has never yet reached Bavaria suddenly, without stages of outbreak on the way. In 1865, when it was so severe on the shores of the Mediterranean, it never reached Munich. Since then our local hygienic arrangements have been greatly improved. These improvements date from the experiences which we obtained in the epidemic of 1852, which was also an exhibition year, and they had a very favourable influence in modifying the invasion of 1873-74. In 1836-37 there died, out of 84,734 inhabitants, 802 persons, equal to 0.94 per cent.; in 1854 there died 2,223 out of a population of 106,715, or 2'08 per cent.; and in 1873-74, when we had two outbreaks, a summer and a winter one, there were 1,466 deaths out of 186,000 inhabitants, or 0.71 per cent. The new water-service in Munich is excellent, both as to quantity and quality, and the delivery to individual houses is now completed. Our drainage system advances rather slowly, but steadily, and the local authorities will doubtless take steps to accelerate it.

As things are at present, even if Munich were without water-supply and drainage, it would not be likely at present to suffer from cholera, for the moisture of the soil, which can be best measured by the ground-water, is at present as high as in 1866, when Munich was threatened by numerous epidemics in Germany and Austro-Hungary, and when the disease was much nearer us than at present. In that year of war there doubtless came to Munich many cholera germs by the medium both of persons and of all other possible things from cholera localities at no great distance. The police-surgeon noted in his journal only nine cases, of which two were fatal, but the city, as a whole, remained free from cholera. Unless we have this year in the coming autumn and winter a long-continued drought, we need have no fear of cholera next year.

Munich certainly does not belong to that class of localities which are severely visited by cholera. The interval between the two first invasions was seventeen vears, from 1837 to 1854; that between the

second two, nineteen years, from 1854 to 1873. Our hope is, therefore, not groundless that we may remain exempt till 1890. And even should it attack us, in spite of everything, we must ever strive to provide it with a less and less favourable soil, and we may then hope that it will pass over us more mildly than before, as experience seems to teach that it will. Let us not, at any rate, insist upon the contagionistic standpoint, which looks upon the unfortunate cholera patient as the infected centre! We shall tend him as before, so that the poor may easily obtain medical help and attention, but we will not shun him. Neither will we tear the well-to-do patient from the bosom of his family; his friends may attend upon him with all love and without any fear, seeing that there is not the slightest danger for them. We may certainly run a risk of being infected in the same place in which the patient became infected, but not from the patient as such. This was shown in the last epidemic, during which all the soldiers who were seized with cholera in the seven barracks of Munich were brought to the one hospital in Oberwiesenfeld, and this hospital in spite of the concentration of cholera cases did not become a centre of infection to others, whilst in previous epidemics the Military Hospital in Müller Street behaved very differently. Port writes on this subject in his report to the Cholera Commissioner for the German Empire, On the Cholera Epidemic of 1873-74 in the Garrison of Munich, and on the Influence of the Military Hospital during the Epidemic,' in the following manner :-'That cholera patients are not dangerous to their attendants has been proved in this epidemic in the Military Hospital, where not a single attendant has even suffered from the slightest choleraic diarrhoea. We cannot ascribe this, however, to the disinfection of every drop of the patient's evacuations. The evacuations are so bulky and so rapidly discharged that to deal with them effectually is impossible: they pour over the bed, the bedding, the clothes of the attendants, and, even if they could be generally quickly removed from the two former, they remain more or less long on the attendants' clothes, seeing that a more frequent change of clothes is either impossible or inconvenient. The following example may be cited in illustration. A cholera patient had so flooded his bed that he might have been said to be swimming in his rice-water stools. In order to give him dry bedding an attendant lifted him up in his arms, whilst another rapidly drew out the wet bedding and put dry in its place. In the short interval the patient evacuated in the arms of the attendant several litres of liquid, which ran down over the arms, trousers, stockings, and slippers of the attendant. Some hours later the attendant was again seen in the same clothing-the dejections had dried on his body and must have been scattered about in dust by his moving about, and must have been breathed both by the attendant himself, and by others, but no case of cholera resulted. Such incidents, more or less modified, are of frequent occurrence in a cholera hospital.' These facts may be cited, in order to counteract the terrifying contagionist notions, which are only too apt to make the attendance more than ever difficult. Let us, therefore, not shun those who are ill with cholera, but let us strive to render our soil in Munich less favourable for disease-poison, and less receptive of cholera-germs; but it must not be done when

Finally, everyone can do much for himself and his family when an outbreak does take place. To be the victim of an attack of cholera it does not suffice that

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the cholera infection should be prepared, and that there should be the required tropical and seasonal tendency, but there must also be the individual susceptibility. In one house there may be twenty or more persons exposed to the same infecting influence, but as a rule only one or two will take cholera. Experience has shown that the greatest influence is exercised by age, robustness, food, bodily and mental strain, clothing, cleanliness, &c. cannot go further into individual dispositions at present, and must refer to a pamphlet on the subject which I published some ten years ago, 'What we may do against the Cholera.' One most important point is to avoid everything that tends to produce looseness of the bowels, the causes of which may vary with the individual. Nothing is so effectual in checking a cholera epidemic as careful attention to the state of the bowels, and medical assistance should be obtained as soon as the slightest premonitory diarrhoea shows itself. It is a great mistake to say that medical assistance is useless, and that because 50 per cent. of cases on an average die, it is immaterial what we do. This is only true for cases which take on immediately the extreme algid form, in which case little can be done; but against the beginnings of the disease, against diarrhoea and cholerine, medical treatment is not powerless, but, on the contrary, most promising. Medical treatment of premonitory diarrhoea is one of the most important prophylactic measures against the development of the severe and dangerous form of the disease.

Our sanitary authority will doubtless provide for quick medical relief, for the most careful watch over the supplies of food, and for everything which previous experience has shown to be important and useful. We may also hope that the enlightenment of the people of Munich will lead them to support loyally the efforts of the authorities to meet successfully any invasion of the disease, which, however, we trust may still be far distant from us.

[Although written in reference to the condition and requirements of the city of Munich, the facts and recommendations contained in Professor Pettenkofer's paper are applicable and valuable to all urban communities. ED.]

MR. MARSH, of the City of London Tricycle Club, has been tricycling in the Alps. The following are the results achieved in this novel and interesting experiment: Mr. Marsh left Lucerne on a tricycle upon Monday, July 9, early in the morning, and ran round part of the lake, and, via Weggen, Greppen, and Kussnach, to Immensee, on Züger See, the margin of which he followed to Art; then, ascending to Goldau, he ran down by Lowerz, along the Lowerzer See to Seewen; thence to Brunnen, on the Uri arm of Lucerne Lake, and by the margin of that lake to Flüelen. The second day was stormy, so he only ran through Altdorf to Amstäg. On the third day he ran up to Andermatt. The day following he ascended the Furka Pass, which is 8,000 feet above the level of the sea; and, descending by the Rhone Glacier, rode to Blitz-nigen, a post-house in the Rhone Valley. Next morning he rode to Brieg, ascended the Simplon, and slept at the Hospice, 6,500 feet above the sea level. On the sixth day he ran down the Simplon Pass to Domo d'Ossola; and on the seventh day by the margin of Lago Maggiore to Locarno.

AND SANITATION.

By W. EASSIE, C.E.*

THE few remarks, which I shall have the honour of making, will bear upon the relationship between geology and sanitation, or what would broadly be called health; they will in no way treat upon the relationship between geology and sanitary engineering, or any of the remedial measures taken from time to time by man, to counteract any unhealthy geological surface presentations. To follow out my subject faithfully, I must also eschew all matters connected with botany, per se, although I may be obliged to refer occasionally to some actions of vegetation, which may affect the healthy conditions of some geological underground formations and superficial deposits. Neither do I consider it within the province of my subject to deal with meteorology or with climatology, because the relationship of these subjects to health is vast, requiring independent treatment, which I trust they will receive at the hands of the distinguished members of the Meteorological Society, who are now members of our Institute. I take it for granted that the earth was made for man, and not man for the earth, and inasmuch as the earth is simply a speck, or almost so, in our solar system, the relationship between health and the meteorological laws bearing upon our earth's crust, really calls for a separate grand division of our subject.

I only seek in this short address to present a few instances where geology becomes the handmaiden of healthiness or otherwise, to the beings born upon its surface; and the time at my command will not allow me to treat of any of the modes in which our terrestrial habitation is fouled by its present or past possessors. I shall say as intimately bound up with the lithological character little as possible upon mineralogy, although it is very and constitution of many of our rocks.

Without going into the question of food production in any detail, there can be no doubt that a man's health depends upon the kind, quality, and quantity of the food which he consumes, and inasmuch as all foods are derived from the earthwhether animal or vegetable-and are obtainable according to the rate of production, it may be wise to consider for a moment the very wonderful powers which some strata possess over others. Let us consider agriculture only. The student will find that the productiveness of soils, as remarked by Mr. Chambers, has no relation to the chronological succession of the various formations. 'The mere geological composition of soils affords no very reliable criterion of economic value. The same rock that produces the almost barren soil of Argyllshire, weathers into the fertile soil of the Channel Isles, and to the old red sandstone is due at once the rich soil of Hereford and Monmouth, &c., and some of the most barren heaths and moors in Scotland.'

The bulk of the tertiary formations are, however, very fertile. With regard to the thin soils overlying the chalk, they are of little value, and do not retain moisture. When the chalk, however, is found naturally covered to some depth with sands and clays, considerable fertility results. The lias and oolitic formations furnish valuable clays of great richness,

* An abstract of the address delivered at the Royal Institution, July 12, at the anniversary meeting of the Sanitary Institute of Great Britain,