a variety of tables might be constructed to exhibit the facts in a condensed form.

10. That an accurate enumeration of the number, ages, &c., of living persons, and an accurate public registration of every birth, every marriage, and every death, with all the information desired relating to each, are absolutely essential as the foundation of every estimation of the sanitary condition of a population; and a sanitary survey, where this is wanting, can be of little value.

11. That for all practical purposes, as means of comparison, the living and the dead may be divided as to the ages, into decennial periods, or periods of ten years each, for those over twenty; into quinquennial periods, or periods of five years each, for those under twenty, and into each year of life for those under five years. This admirable division has been adopted in England, (see table, p. 34.) For special purposes three divisions should be made;-of those under 15, of those between 15 and 60, and of those over 60,-as the Dependent, the Productive and the Aged classes. The division, sometimes made between those under 20, and over 20, as "boys and girls," and "men and women;" or as "children and adults," is indefinite, unmeaning, and useless; as are also the ages 4, 8, 14, 16, 21, and 45, which have been sometimes used as dividing points.

12. That to secure such uniformity at different places and at different times, in the abstracts of the facts concerning the living inhabitants, and the dead, that each may be accurately compared together, both should be made under the superintendence of one agency, and that agency should be the General Board of Health.1

XV. WE RECOMMEND that provision be made for obtaining observations of the atmospheric phenomena, on a systematic and uniform plan, at different stations in the Commonwealth.

The atmosphere or air which surrounds the earth is essential to all living beings. Life and health depend upon it; and neither could exist without it. Its character is modified in various ways; but especially by temperature, weight, and com

1 Those who may wish further information on the subject of Registration of births, marriages and deaths, may consult the books already referred to, in notes pp. 30-36, 55, 128.

position; and each of these modifications have an important sanitary influence.

The temperature of the atmosphere is measured by the rise and fall of the mercury in the thermometer; and it varies greatly in different times and seasons, and in different places. In Massachusetts, it sometimes rises 100 degrees above; and sometimes sinks to 20 or more below zero. Health is often affected when extremes of heat or cold are long continued, or when the changes from one to the other are sudden.

The weight of the atmosphere is determined by the rise and fall of the mercury in the barometer. This rise and fall is about 3 inches-generally from 28 to 31. It is seldom more than 2 inches in the same locality; and sometimes not more than 1. In Massachusetts the rise has been known to be as high as 31.11, and the fall as low as 28.47, showing a difference of 2.64 inches. The weight of the atmosphere at the earth's surface is 14.6 lbs. to the square inch. Allowing the surface of a man's body of medium size to be 15 square feet, or 2160 square inches, he suffers the enormous pressure of 31,536 lbs., or more than 15 tons! It is, however, generally unperceived, because the pressure is equal, within and without. It is only by its variations that we are affected. But these variations, when analyzed, will appear immense. Each fall or rise of one tenth of an inch indicates a difference of about 100 lbs. A fall of of an inch shows the removal of a pressure of about 100 lbs.;, 200 lbs.; fa, 500 lbs.; 1 inch, 1,000 lbs.; 3 inches, 3,000 lbs., &c. If these variations were sudden, inconvenient and fatal consequences might follow. When the pressure is removed we do not feel light as we should do by the removal of the same number of pounds of iron or other substance; but we feel sluggish, heavy and spiritless, owing to the excessive expansion of the fluids of the vessels, the nerves, and other living fibres, produced by an excessive expansion and escape of a portion of the air incorporated within them.

The atmosphere is composed of two principal gases, and they exist in all places in nearly the same proportions-about four-fifths of nitrogen and one-fifth of oxygen. The latter is the principal supporter of life. Other gases may also be dif

fused in greater or less quantities. Brand's Encyclopædia of Science states the average ordinary composition per cent. of the atmosphere as follows:

Aqueous vapor exists in greater and more varied proportions than carbonic acid gas, though the quantity of that gas is very different at different times and places. Sulphuretted hydrogen, ammonia, and other gases, may also be diffused in quantities so great as to be detected by the senses, or by chemical analysis, or so minute and inodorous as to escape detection, and in either case may be the cause of disease. Some idea may be formed of the almost infinite divisibility of matter, diffused in the atmosphere, from the fact that the hound in the chase discerns the track of man and animals by the odoriferous particles thrown off from their foot-prints; and that we detect the odor of musk, notwithstanding the single grain from which it proceeds was deposited twenty years previous, and has since been constantly diffusing its particles in the surrounding atmosphere!

The atmosphere is corrupted in various ways. Man himself cannot breathe the same air twice with impunity. Every minute of every day he appropriates to the vitalization of his blood 24 cubic inches of oxygen, and supplies its place with 24 inches of carbonic acid gas. When present in large quantities, from whatever cause produced, carbonic acid gas is destructive of life. Charcoal burned in a close room is an illustration. Some other gases are also very destructive. The experiments of Thenard and Dupuytren proved that birds perish when the vapors of sulphuretted hydrogen and ammonia exist in the atmosphere to the extent of a fifteenth thousandth part; that dogs are deprived of life when the air contains a thousandth part; and that man cannot live when the air he breathes is im

pregnated with a three-hundreth part; and suffers in corresponding degree when a less proportion of these poisonous gases exists. Persons frequently fall dead when entering a well, vault, tomb, sewer or other place, filled with these gases, or with stagnated air in which are diffused emanations from decomposing animal, vegetable or mineral substances.

Such are a few only of the facts which illustrate the important agency of the atmosphere in the animal economy. What that peculiar condition is which produces a specific disease, or what changes produce different diseases, are as yet unknown; it has not been ascertained, "because meteorological science, as connected with the propagation and spread of disease, is as yet in its infancy. We have, indeed, some knowledge of the influence of two of the obvious conditions, namely, those of heat and moisture; but of the action of the subtler agents, such as electricity and magnetism, the present state of science affords us little information. Still there are unequivocal indications that there is a relation between the conditions of the atmosphere and the outbreak and progress of epidemic diseases, though we are as yet ignorant of the nature of that relation."

“The earth, it is well known," says the Registrar General, "is surrounded by an atmosphere of organic matter, as well as of oxygen, nitrogen, carbonic acid, and watery vapor. This matter varies and is constantly undergoing transformations from organic into inorganic elements: it can neither be seen, weighed, nor measured. The chemists cannot yet test its qualities. Liebig, with all the appliances of the Giessen laboratory, cannot yet detect any difference between the pure air of the Alps, and the air through which the hound can tell a hare, a fox, or a man has passed; or the air which observation shows will produce small-pox, measles, scarlatina, hooping cough, dysentery, cholera, influenza, typhus, plague. These matters may either be in a state of vapor, that is elastic, or inelastic; or like water, they may exist in both states. They are most probably in the state of suspension; hang, like the smoke in cities, over the places in which they are produced, but are

'Report of the General Board of Health on Quarantine, p. 10.

spread and driven about like vesicular water in clouds. stream of aqueous vapour of the same elasticity from the Atlantic, passing over England, is, in one place, perfectly transparent; in another, mist; in another, rain: so clouds of epidemic matter may fleet over the country, and in one place pass harmless by, in another destroy thousands of lives. The emanations from the living, the graves, the slaughter-houses, the heaps of filth rotting, the Thames,-into which the sewers still empty,— raise over London a canopy which is constantly pervaded by zymotic matters; in one season this, in another that, preponderating."

Although we are as yet uninformed on this subject, it is unreasonable to suppose that we shall always remain so. It opens a vast field for examination, which is as yet almost entirely unexplored; but it promises results of great value and importance to science and to human life. The meteorological observations, which have hitherto been made in this country, have been published rather as contributions to general science, than to show their specific relation to health. In England, and in some places on the continent of Europe, these observations are made with more care, and for a more specific purpose. For several years past Mr. Glazier, director of the Royal Observatory at Greenwich, has published his meteorological observations and remarks on the weather, in connection with the returns of the Registrar General of births, marriages and deaths.

In Edinburgh, particular attention has been paid to the influence of atmospheric causes on the production of disease. Dr. James Stark, in his Report on the Mortality of Edinburgh and Leith, for the last quarter of 1847, (pp. 4 and 5) says, that the "Influenza suddenly attacked great masses of the population twice during the course of November; first on the 18th, and again on the 28th of the same month. In both these cases it appeared after a keen frost, and an excessively damp thick fog, which came on rather suddenly after a few days of very mild weather. The disease was therefore clearly dependent on atmospheric causes."

"Though influenza was so exceedingly general, it did not of itself materially increase the mortality during November; but this disorder and its atmospheric causes greatly increased the mortality of all other diseases. So much has this been the case, that from the 18th of November, when influenza first appeared, the mortality daily increased till it reached 61 deaths on the 30th day of the month. In fact, influenza and its atmospheric causes appa rently attacked the weak point in every individual, be that the lungs, bowels, or other or gans, and hastened to a fatal termination cases which, in ordinary seasons, might have survived for months or years."

Again, in his Report for June, July and August, 1848, the same author says:-"The influence of weather on disease was, however, still more strikingly manifested in regard to bowel complaints and affections of the organs of digestion, registered under the heads of diarrhoea, dysentery, cholera, teething, inflammation of the bowels, &c. During the heats of summer and autumn, these diseases in general become exceedingly prevalent and fatal, and it has been the too common belief that the use of fruit and vegetables was the cause of these affections. The mortality of these diseases, however, during the above months, most satisfactorily proves that these diseases do not depend on, or are caused by, the use of fruit