REFERENCES AND NOTES TO PRECEDING TABLE.

Nos. 1 and 2, Germantown, Pa. From the same well. Taken nine days apart, during the prevalence of the epidemic. The "total solids " recorded under No. 1, was from still another sample. A child living some distance from the place drank some of the water and sickened in consequence, otherwise the cases were among those living in the neighborhood and using the water. Well, ten feet from a brick sewer, which was somewhat choked at that point.-Chemical News, xliii., 183.

No. 3, Fairhaven, Mass.-First case, September 30th; second case, October 3d; third case, October 6th; fourth and fifth cases, October 7th; sixth case, October 8th; seventh case, October 9th; eighth, mild case, middle of October.

The entire family. No others took the disease except the nurse and her mother who nursed her. Neither of them drank any of the water. Well, one hundred feet from privy vault. Connection between the two proved by throwing salt into the privy vault and finding an increase in the chlorides in the well a few days later.-"Massachusetts State Board of Health Report for 1879," Supp., p. 270.

No. 4, Scituate, Mass.-Examination made about a month after the disease prevailed in the family and among neighbors who drank the water. None of the cases fatal. Only three other cases (a mile away) in the town previous to the outbreak at this spot. Well, thirty feet from privy. Water contained bacteria and infusoria.-" Massachusetts State Board of Health Report for 1879," Supp., p. 273.

No. 5, Grouville, Island of Jersey.-Female Orphans' Home. House isolated. Well, sixty feet from an old cesspool used only for urine and soapsuds at the time of the outbreak. Disease apparently generated de novo. No new cases occurred after the pump was removed.-Chemical News, xl., 97.

No. 6, Eagley, near Bolton, England.-Brook received the excreta of operatives at a factory, among which one man had typhoid fever. Water said to have been used only to wash the milk cans. No one affected except those who drank the milk from this dairy." Massachusetts State Board of Health Report for 1877," p. 123.

No. 7, New York, Manhattan Island-Asylum. --Well over one hundred feet deep. No ostensible cause for the appearance of the disease, except communication through the drinking-water. Sewage appeared to reach the well in about two hours from the time of deposition in the sewer. Connection between sewer and well proved by application of the "lithia test."

No. 8, Broad St., St. James Parish, London, England, 1854.-The number of cases is unknown; 609 deaths are believed to have resulted directly or indirectly from drinking the water of this well. Of two factories situated side by side, the workmen in one drank the water and were almost all attacked, while in the other, other water was drunk and the workmen escaped. An old lady, living entirely outside of the affected district, drank the water, as did also her niece living with her, and both died of the disease. No one else in their immediate neighborhood was attacked. The well was closed up at the time, but opened a year after the outbreak and pumped out, after which this sample was taken.—Sixth Report Rivers Pollution Commission," p. 497. No. 9, New Orleans, La.-Odor of the water, like swamp water. Cistern (wooden), old and rotten. -"Report on the Water Supply of New Orleans and Mobile. Smart.

National Board of Health Bulletin," vol. i., 317.

Dr. Chas.

No. 10, Mobile, Ala.-Case similar to the last. With regard to this, Dr. Smart notes particularly that the fever "prevailed in the absence of prominent sources of malarial exhalation to account for the presence of the disease."- "National Board of Health Bulletin," i., 317.

No. 11, Rye Beach, Mass.-Digestive disturbance caused, "characterized by a sensation of giddiness and nausea, vomiting, diarrhoea, severe abdominal pain, all of which was accompanied by fever, loss of appetite, continued indigestion, and mental depression." Ice taken from a shallow pond choked with marsh mud and decomposing sawdust, and used in the hotel where all the cases occurred.-"Massachusetts State Board of Health Report for 1876," p. 467.

VOL. II.-28

Testing Connection of Well and Cesspool, etc.-Wells in the neighborhood of houses are especially liable to contamination from the cesspool, drain or privy vault. The most convenient mode of testing whether any connection exists between the well and such possible sources of contamination, is by adding to the cesspool or privy vault some soluble compound, and testing for its presence in the well. Sometimes large quantities of salt are thrown in, and the well water is then tested for an increase in the proportion of chlorides. This method may be affected by temporary or local conditions, and is, on that account, inferior to the more expensive method of throwing soluble lithium salts into the cesspool, sewer, etc., and testing the water afterward for the presence of lithia. Except in the water of mineral springs, lithia is of rare occurrence; moreover, very minute traces can be detected by the spectroscope, and though much of the lithia is probably absorbed by the soil, enough will usually work its way through if the suspected connection exists.

ICE.

A few words on the impurities in the ice so lavishly used in this country for cooling our beverages in hot weather. Cases of illness have occurred which have been traced to the use of ice in this way, though not very frequently. The commonly received impression that water in freezing not only rejects all impurities, but that any germs if frozen into it are necessarily killed, requires some correction. Water in freezing will enclose particles of organic or other matter which may be suspended in it, and almost any microscopist can testify to the persistent vitality of many of the lower forms of organisms, even after being imprisoned for a long time in blocks of ice, perhaps benumbed and dormant until released, but living. The general rule that "a pond or river which is unfit as a water supply should not be used as a source of ice supply "" is a good one, but often disregarded.

2

As regards the chemical analysis of ice, it should contain no perceptible suspended matter when melted, very little dissolved matter, or chlorine, and the albuminoid ammonia should not exceed 0.005 part per 100,000.3

CONCLUSION.

In discussing the question of water supply reference has necessarily been made to certain theories which are now engaging the attention of sanitarians, and which (inasmuch as they are theories or hypotheses) have both strong supporters and vigorous opponents. Such are: The germ theory of disease; the "drinking-water theory;" the purification of rivers by flow; the generation of diseases de novo; and finally the value of certain of the chemical tests applied to water.

It must be remembered that these theories have been advanced after a careful study of numerous facts, and whether true or not as they are now stated, they cannot be regarded lightly. Future study of sanitary science may modify these views as at present held by their supporters, but it will be always desirable to keep on the safe side in selecting a location for our dwellings or deciding upon a water supply for our households, and we should not unnecessarily risk the health or lives of our families.

1 Nichols, Water Supply, p. 132.

2 Ibid., p. 52.

3 Ibid., p. 54.

THE CHARACTERS AND DISTRIBUTION OF

AMERICAN SOILS.

BY N. L. BRITTON, PH.D.

THE soil is generally understood to be the upper, superficial portions of the accumulations of loosely consolidated materials, which in most regions form the surface of the earth. In this chapter it will be so considered. It is the part of the earth's crust which, directly or indirectly, supports vegetable and animal life, and is thus of immense importance to mankind. The thickness of this superficial material varies greatly in different localities; in some we find very little, or, indeed, none at all, the rocks coming directly to the surface; but such are limited in area and mostly confined to the slopes and summits of mountains; nearly everywhere there is an appreciable quantity of soil, and the accumulations are occasionally over one hundred feet deep.

To render what follows intelligible to all, it has been deemed advisable to preface this dissertation with some of the leading facts relating to the origin, structure, and constituents of soils in general.

STRUCTURE AND COMPOSITION.

The soil is constituted of variously sized fragments of mineral and organic matters, and its character depends on the relative abundance of the different constituents, the dimensions of the fragments, and their greater or lesser consolidation. It is invariably permeated to some extent by water and air, and the quantity of these fluids depends on the permeability and the absorbing property of the soil, which vary greatly. The size of the component fragments is very variable, and ranges from microscopical particles, which make up the greater part of the mass, to boulders of huge proportions.

Mineralogically considered, it consists primarily of sand and clay; these constituents occur either alone or intermingled with each other in various proportions; they are often accompanied by pebbles, or even large stones of different kinds of rock, and generally by small amounts of other inorganic or organic matters. Most of the latter is derived from plants and is known as peat, humus, etc. Clay and sand are, however, the bases of all soils, and one of these minerals is always present.

ORIGIN OF SOILS.

All soils have been derived from previously existing rocks by processes of decay and disintegration acting through immensely long periods of time, and are still forming wherever rock masses are exposed to agents which produce and forward these changes. The materials resulting from

these processes are found either in situ, where the rocks furnishing them were formerly situated, or at a distance from the parent rocks, and this commonly many miles.

Among the most widely acting and important of the agents which produce decay in rocks are the following:

(a) Percolation by Water, and the consequent solution and removal of some ingredients.

(b) Frost, which promotes disintegration by the formation of ice from the water contained in rocks, the expansion accompanying this phenomenon forcing fragments loose.

(c) Oxidation of certain constituents, particularly the compounds of iron in pyrites, hornblendes, etc.

(d) Kaolination, by which the feldspars are reduced to clays.

(e) The Action of Vegetation, plants having the habit of forcing their rootlets into minute crevices, and by subsequent growth and chemical action disintegration ensues.

(f) Erosion by Water or Ice.-The destructive action of rain, currents of water, ocean waves, etc., on rocks is continually in progress. Ice erosion, now confined to the polar regions and to a few elevated mountain chains where glaciers yet occur, was a most important agent of soil production at a former period of the earth's history.

These agents of rock-destruction act independently or in conjunction; there are also other less important ones contributing to produce the same results, which need not here be discussed.

The most important of the agents which tend to remove and distribute the disintegrated materials resulting from the above-enumerated forces, and to whose action many of our soils owe their origin, are:

(a) Water. The transporting power of water is well known. The products of rock-decay become washed into streams, and the more comminuted portions, the clays and finer sands, are carried by them into the rivers, and in part deposited along the valleys, forming the rich floodplains which in many cases extend over hundreds of square miles of territory on each side of the river proper. Deltas have a similar origin. The continued beating of waves against the coasts gradually promotes disintegration, and much of the sand thus produced is ultimately driven upon the shore to form beaches.

(b) Ice.-At present the work of ice in this connection is insignificant. But during the period of past time known to geologists as the Glacial Epoch, it played a grand part in soil production. During this period a great ice-sheet, many hundreds of feet in thickness, advanced over North America from arctic and sub-arctic regions, extending southwardly to the coast of New England and Long Island, the Narrows of New York Harbor, and thence across the continent, its southern margin following approximately the fortieth parallel of north latitude to the Missouri River; thence bending northward it joined with another sea of ice, which descended from the Rocky Mountains as far south as the thirty-sixth parallel. Local glaciers were also developed on the Sierra Nevada and along the Pacific coast.

This ice-mantle covered all explored parts of North America north of the lines above described, and it has left undeniable proofs of its work on the rocks which it smoothed and striated, in the immense erratic boulders and in the soils which occur within the areas traversed. In its slow southward movement it carried an immense amount of débris, torn from the rocky strata over which it passed, and during the ensuing melting this burden was left scattered over the areas occupied by the ice. The melt