TABLE FOR FINGER PUMP commonly used, the ball marked 2 oz., but only about two-thirds of this actually used :—

The number of ballfuls required to produce the precipitate being counted, on referring to the table the percentage of carbonic acid in the air is at once seen.

An easy method of finding the precipitate for comparison is by shaking half-an-ounce (14·17 cub. cents.) of baryta water in a bottle with 23 ounces of Manchester air or nearly 30 ounces of London air (elsewhere according to residence).

Experiments made with this apparatus show it to be extremely delicate. The carbonic acid in the air of a room can be estimated in a few minutes. For very bad air smaller balls are used, but in all cases only half-an-ounce of baryta water.

The second way of using the minimetric method was partly described in the report on the air of mines, and long tables were there given both for baryta and lime water. It is more particularly adapted for use in houses and workshops.

Suppose, if we desire to know if the air contains more than 0.04 per cent. of carbonic acid, we fill a bottle containing 5-422 ounces with air, by pumping or otherwise, and shake in it half an ounce of baryta water. If there is any precipitate at all the amount of carbonic acid in the air is above 0.04 per cent. This would indicate that the air is less pure than outside.

If we allow 0.06 per cent. of carbonic acid in a room, we take a bottle of the size of 3.281+ounce = 3.781 ounces (or 107.19 cub. cents.), and if, after a trial as above, we find a precipitate, however small, or even a slight milkiness, the air is deteriorated beyond 0-06. This relates to dwelling houses.

If for workshops we allow per cent. (0.25) a bottle of 0.788+ounce = 1.288 ounces (or 36.51 cub. cent.) is sufficient. If per cent. is allowed (0.50) a bottle of 0.394 × ounce = 0.894 ounces (or 25.34 cub, cents.) is enough.

Both of these two last sizes of bottles are small enough to be

carried in the waistcoat pocket. The addition of the ounce is for the space occupied by the baryta water.

Lime water, being very common, will probably be often substituted for baryta water. The experiment is exactly the same, only larger bottles are required.

0.06 per cent. carbonic acid in the air gives us precipitate or milkiness when ounce of lime water is shaken in a bottle of air containing 10567 ounces (=299.57 cub. cents). 0.25 per cent., 2.916 ounces (=82.67 cub. cents). 0.50 per cent. 1.708 ounces (=48.42 cub. cents.).

By this simple method the greatest refinement may be attained. Of course care must be taken to have the baryta or lime water perfectly clear to begin with.

The author said he had not used these methods for purely scientific investigations.

HEALTH OF TOWNS.

The Danger of Deterioration of Race from the too rapid increase of Great Cities. By JOHN EDWARD MORGAN, M.A., M.D. Oxon. Physician to the Salford Hospital, Hon. Sec. Manchester and Salford Sanitary Association.

TH

HOSE who have studied the distribution of the population of Great Britain, during the last fifty years, cannot fail to have observed on the part of the labouring classes an increasing tendency to mass together, and either to form new centres of industry, or to swell the population of those already existing. The desire of raising themselves in the world, keeps constantly urging vast numbers of the dwellers in rural districts to emigrate to the nearest town; where wages are higher, and the conditions of life apparently more attractive. To this cause, more than any other, is to be attributed that extraordinary development of every branch of our manufacturing industry, which induces even the most distant nations to look to this country as to the great mart which, however varied their wants may be, can best supply them. In this national prosperity, in successful competition with numerous rivals, and in the acquisition of immense wealth, we see much that is calculated to gratify our vanity as a people. Yet at the same time arises a momentous question-" May not nations, like individuals, curtail their day of power in the world's history, by overtaxing the physical and mental energies at their disposal, thus prematurely consuming that national life-blood on which permanent greatness mainly depends?"

Among the many important questions connected with this widespread migratory tendency, there is one, which, to sanitary reformers,

must needs prove peculiarly interesting. I refer to the influence which it is likely to exert on the public health. As Honorary Secretary of the Manchester and Salford Sanitary Association, I have had occasion to draw up weekly and quarterly reports on the health of Manchester; and at the same time, as physician to the Hospital and Dispensary of Salford, I have had constant opportunities of gaining an insight into the physical condition and mode of life of that portion of our industrial poor who pass their days amid the restless turmoil of a city life. In this manner, my mind has been led to the consideration of this question, and in the remarks which I am about to make, I shall have for the most part to record conclusions, not based on mere hearsay testimony, but the result of my own personal observation.

In the first place, then, in my professional intercourse with the poor, I have been much struck by the singular want of stamina which characterises them as a class, manifesting itself either in the gait, the bearing, the voice, or the frame. Instances in which the muscular system is fully developed or well strung, are remarkably rare. Few are men of that calibre from which we might expect either vigorous and healthy offspring, or arduous and sustained labour. Cases of deformity, accompanied by actual distortions, are by no means uncommon; while minor physical defects, many of them denoting no trifling constitutional ailments, are deplorably frequent.

The pulse that faithful index of the heart-tells of a want of power in the great propelling organ. The most trivial exertion, no less than the slightest excitement, renders the variations in its beat unnatural and rapid. The irregularity of the circulation is further evinced by the coldness of the extremities, the attacks of vertigo, and the prominent and tortuous veins. The blanched lips and the colourless cheeks plainly indicate the impoverished state of the blood. While attacks of neuralgia, a quiveringly protruded tongue, and dilated pupil, denote the absence of that well-balanced tension of the nervous system, on which the easy and harmonious working of the frame so largely depends. In others, again, the teeth are no sooner developed than they begin to decay, enlarged glands protrude from the neck, the skin looks dry and parched, and the hair scanty and withered. Such is a faithful description of the great majority of the patients who solicit medical advice at our hospitals and dispensaries. Additional confirmation of what I have stated will be found in the large number of military recruits who fail to come up to that standard of bodily fitness which the medical referees are instructed to insist upon. I have been informed by an officer, specially associated with the superintendence of this service, that in some of the manufacturing districts, four out of every five men sent up by the sergeants for medical inspection are rejected, on the ground of physical disqualification. Let us next proceed to inquire into the causes of this degeneracy, and the extent to which it prevails; and in so doing, let us specially consider how far it is to be ascribed to the influence of a Steam re with the pair r desses I Love fie.

quently interrogated them respecting their own birth-places and those of their parents; and, in numerous instances, have been much struck by the difference in physical development between the indigenous population and those persons who have migrated into the town in adult life. It has further appeared that, as a rule, this deterioration has, to some extent, been proportioned to the length of time which has elapsed since my patients, or their ancestors, became exposed to the lowering influences of a city life and in-door employment. I cannot help thinking, that the extent to which these influences are undermining the vitality of the nation, is not in general brought forward in so strong a light as the facts bearing on the question undoubtedly warrant. In examining it, under a few of its aspects, it is, in the first place, necessary to show clearly the extent to which the tide of emigration is constantly flowing from rural districts to populous centres. This I have endeavoured to set forth in the accompanying table. It tells at a glance the composition of the four chief cities in England-London, Manchester, Liverpool, and Birmingham-the number of persons over and under twenty years of age, and the proportion of them which, at the taking of the last census, was described as either exogenous or indigenous, is tabulated and compared.

I. TABLE showing the NUMBER of IMMIGRANTS under and over 20 Years of Age, in the Four largest Towns in England.

What then, are the results?-1st, as regards London-of the population under 20, 74 per cent. were born within the boundaries of the capital. The remainder were composed of immigrants, supplemented (though to an inconsiderable extent) by foreigners. On turning to adults, however (those who had attained the age of 20 and upwards) the proportion of aliens proved far more considerable -amounting to 53 per cent., while the natives did not exceed 46 per cent. In Manchester (the second city on my list), 84 per cent. of the young were born in the county of Lancaster, but only 50 in every 100 adults. Lastly-of the grown-up population in Liverpool, no

fewer than 62 per cent. were born out of the county, and afterwards settled in the town.

Two important facts are directly deducible from this table; 1st. the extent to which our large cities are recruited by immigration, and 2ndly, that the great majority of the incomers are men and women in the prime of life.

Let us next turn to inquire into the sources from which this extensive alien population is derived, and first, as regards that portion of it which is settled in London. Whence came those 864,000 grown-up men and women on whose lives and labour the prosperity and greatness of the empire city so largely depend? The majority of them certainly did not migrate there from our great centres of industry, where their constitutions might have suffered from long hours of confinement. Men of this class constitute but a small item in the alien element of the population of London-that such is the case may be gathered from the statistics contained in my second table which specifies the particular counties in which these aliens were born.

II. TABLE showing the EXOGENOUS POPULATION of LONDON.