B. The necessaries of life for the individual man
II. Water
In towns the air generally is the most contaminated, owing to the large traffic and the great number of factories; the purest air and the healthiest atmosphere is there, where little dust is raised, e. g. in forests and on the seashore.
§ 39. The climate. Each place on the surface of the earth stands under the influence of its peculiar meteorological conditions, which are also of importance for the health of man. The sum of these meteorological conditions is called the climate of the place. This is judged on the one hand by the average temperature; on the other hand atmospheric pressure, moisture, direction of the wind, rain or other de-posits are to be considered. Besides, the frequency of a cloudy sky is of importance, as a clouded sky averts the rays of the sun and somewhat prevents the diffusion of the heat of the earth to the higher layers of the atmosphere.
In general the climate is determined by the geographical position of a place, as the average heat of the atmosphere decreases from the equator to the poles. We distinguish the tropical from the temperate and polar climate. The altitude of a place, through the difference of the atmospheric pressure gives a peculiarity to the high climate or the mountain climate as peculiar from the climate of the valley. A relatively small variation of the heat of the atmosphere and a considerable moisture of the air besides frequent rain is a distinguishing characteristic of the sea-coast climate from the inland or con-tinental climate. Lastly the climate of a place can be essen-tially different from the neighbouring places, if large forests or mountain ranges afford a protection against the wind, in which the neighbouring place takes no share.
II. Water. 43 We satisfy our need of water partly by our victuals, which contain water, but for the most part by beverages, the consumption of which is caused by the feeling of thirst.
§ 41. Drinking water; its necessary properties. Nature directly offers us drinking water as the cheapest and simplest beverage, but every water is not fit for this purpose. In general we rightly only regard as good for drinking water which is clear, colourless, free from undissolved, swimming matter, which does not possess a strange smell or taste, which is cool and tastes refreshing.
We call water ,hard" which contains a large proportion of lime or magnesia salt; in opposition to this water is called ,soft", which is poor in such salts. ,Hard" water, which is more pleasant to our taste than ,soft" water, is not suitable for washing, because it dissolves badly soap and some dirt-containing substances; also it cannot be used in cooking, as it deposits its salts on the cooking-vessels as so-called ,fur", and cannot extract from some food-stuffs the nutriments so well, as ,soft" water.
From a hygienic point of view the most important pro-perty demanded from drinking-water is that it shall not con-tain any impurities injurious to health. The above mentioned properties of good drinking- water will generally be some guarantee of its purity; still, water which is unobjectionable as regards appearance, taste or smell may be the carrier of admixtures, injurious to health. Particularly every class of water contains a smaller or greater number of minute living bodies, only visible with a microscope, which are called micro-organisms. For the most part these are harmless; still ex-perience has taught that the microbes of contagious diseases can also get into water used for drinking and by means of it can become disseminators of epidemics. In order to obtain a reliable judgment on the fitness for use and innocuity of water, the amount of dissolved matter it contains, as well as the micro- organisms, especially so- called bacteria and the species of the latter must be determined by experts.
§ 42. The SOlll'Ce of water. Rainwater. Cisterns.
Generally by a knowledge of the source of the water we gain already some points for judging of its fitness for use. We distinguish between rain-, spring-, subterranean- and surface water.
Deposited water or meteoric water ( cf. § 36) reaches the ground mostly as rain, is poor in saline matter and in con-seqence very ,soft". As the deposits cleanse the air, - so to say - the first water, falling in a shower or snowfall contains frequently impurities of different kinds, which accord-ing to their qualities putrefy under the influence of micro·
organisms; later falling water it purer. Through rain-water on account of its ,softness" is not very palatable, and may even cause digestive disorders, if taken in large quantity; still those who live in waterless regions are compelled to collect it in vessels or in walled cavities, (cisterns) and to use it as drin-king-water; such cisterns ho-wever are easily exposed to contaminations from the sur-face of the earth.
§ 43. Subterranean wa-ter and springs. If the rain-water falls on pervious soil, like gravel or sand, it trickles into it and leaves behind in the upper layers of the soil, as in a filter the undissol·
ved impurities, brought with
Fig. 16.. .. ... lnemmc:ou wale•· lllldc•· pl"eS III'C it from the air or the earth's
spout s JJI :l Jf' L through the :.p C I'I~ II 'C, hOt"(l'd i n
"" i111pervious ln)'er. surface. Here the water at the same time takes up cer-tain soluble constituents of the soil as well as carbonic acid from the subterranean air, which is in the pores of the ground. The water, now containing free carbonic acid is able to dissolve partly more earth-minerals, consisting of chalk and magnesian com-pounds and gradually acquires a ,hardness", corresponding to the quantity of mineral matter received. As soon as in the course of its infiltration the water arrives at an impervious soil, (rock, clay or loam) it spreads according to the slope of the soil as sub-terranean water. If the impervious layer is of an undulating form it collects in its deepest places as a subterranean pool or lake; if it has trickled through on the surface of a hill or montain, it can, by flowing down the impermeable layer, reach the bottom of the montain and there appear on the surface as a spriug. If the water in its course flows into a space,
II. Water. 45 bounded above and below by an impervious layer, we sec it often spout forth from the orifice with great force, some-times in a large jet, if the upper layer is pierced from the surface of the earth. (Fig. 16.)
Owing to the filtering nature of the soil subterranean water as a rule is free from bacteria. It contains carbonic acid and mineral substances, has a refreshing taste and on account of its purity is well suited as drinking water. Ex·
ception must be made of the water of the so-called ,Rasen-quellen' (turf springs) i. e. of such springs, where the water collects so closely under the surface of the earth, that it is neither reliably filtered by the earth, nor sufficiently im-pregneted with carbonic acid and minerals, nor far enough removed from the influence of solar and atmospheric heat.
The water of the subterranean wells coming from a moderate depth rises slightly in temperature during the heat of the summer, but is as a rule fit for use; the water of the mineral spr'ings, coming· from a great depth remains uniformly cool, possesses a pleasant refreshing flavour and is free from bac-teria. The last mentioned water can only acquire unhealthy qualities by being contaminated at the spot, where it appears as a spring, or where it is made accessible for usc by the buildings near the wells.
§ 44. Spring-water pipes. Well-lUachinery. Contamina-tion of spring-water may occur, if the water is first conducted into collecting basins or well-chambers in order to be drawn out of these for use or to be conducted by means of pipes to human settlements. In order to prevent pollutions of their contents the collecting basins-should be placed as far as pos-sible away from human habitations, and to ward off lateral influxes impervious walls with edges, overhanging the surface of the earth as well as a thick movable cover should be pro-vided. Waterpipes ought to have impervious sides and abso-lutely tight joints.
We distinguish flat- or surface wells from deep wells (Fig. 17).
The water of the surface wells flows from the subterranean water of the uppermost layers of the earth, and hence easily contains injurious ingredients in populous places, the subsoil of which is polluted by the refuse of human habitations.
The water of deep wells in usually, free from bacteria and decomposed elements of organic matter; but its utility as
drinking water, especially in North Germany is more frequently injured than the water from surface wells by a mixture of iron salts, which imparts to the water an inky taste and in the open air causes a gradual deposition of a brownish slime.
Various devices have been invented for freeing the deep water from these iron salts.
Owing to the unsuitable construction of a well its water frequently is of a bad quality; particularly the so-called bucket-and pump wells prove objectionable. These are built, by ex-cavating the earth down to the water bearing strater and by supporting the sides of the excavated hole by means of beams of timber or masonry. In the hollow or shaft, thus constructed the deep water collects on the floor or ,bottom' and is raised by means of buckets
(dmw-!Cnlh) or pumping machines (purnp-wells). If the sides nre not quite tight, or if the well is not properly covered- sometimes there is no covering at all -these wells are in a high degree exposed to pollu-tion from the surface or
Fig. 17. S11r(m'< aml rlt•ep 111•11.•. the latera} layerS Of earth.
This happens particularly, if these shaft wells, as is frequently the case in country districts are placed in the neighborhood of dung heaps or cesspools (which are not quite tight) so that the contents of the latter find their way to the water in the well. (Fig. 18.)
Even very tight walls of the well give no reliable secu-rity for a continued pusecu-rity, as the substance, used for making tight the walls soon gets cracked and these cracks are usu-ally discovered when the pollution of the water ia the well has been already accomplished.
Greater security is afforded by Pipe wells (Fig. 19) Abes-synian or artesian wells; they consist of an iron tube, which is driven into the earth down · as far as the strata, containing the deep water, and is provided with a pumping arrangement
II. Water. 47
at its upper end. The impenetrability of the metal sides excludes every lateral influx into the water.
§ 45. Surface Water. In some places the opening up of the deep water is impossible, or very difficult; either be·
cause its basin lies too deep under the surface of the earth, or because the subsoil consists of rock, and cannot be bored without great difficulty and expense; or because the
ground-J." j '· 1 . Pollut.iun of a d1·aw-wcl1 hy 1hc couwnts of o. ncighlJouring ccs~- povl.
water is unfit for use owing to the salts it holds in solution.
If in such places springs are not available, the inhabitants are compelled to use surface water. By this term is meant the water of streams, rivers, lakes, ponds and generally all such water, the level of which is on the surface of the earth. Its value as drinking water is much inferior than springwater or groundwater; it also does not possess in summer the refresh-ing coolness, as it is exposed direct to the influence of the atmosphere and to the rays of the sun; it is also poor in carbonic acid and mineral substances and generally contains
impurities. To the latter belong the excreta and debris of aquatic animals and plants, but particularly the refuse of the organic world, living on the borders of the water.
Frequently among the domestic refuse the excreta of sick persons containing the germs of infections diseases are carried to the water. In certain circumstances manifold diseases, epi-demics of typhoid and cholera can be caused by the use of
} 'ig. 10. l'iJIC wells.
surface water for instance: the devastating cholera epidemic which visited Hamburg in 1892 was traced to the unfiltered drink-ing water of the town, taken from the Elbe.
In many stagnant, or sluggishly slow flowing bodies of water such as ponds, ditches, canals or small rivers the result-ing pollution shows itself frequently already in the muddy colour, the foul smell and taste of the water; investigations show, that in water in this state there may be found microorganisms up to 100 000 and more per cubic centimetre. The influence of the contamination is diminished, the greater the surface of the water is and the quicker the water is carried away by the current. At some distance from such con-tamination the water is usually found pure again, it is assumed, that it is able to rid itself of its impurities by means of the so-called self-purification. This process takes place on the one hand through the de-position of the filtry matter on the bottom and on the banks of the river, on the other hand by the decomposition of the for-eign ingredients, certain noxious species of bacteria are able however, under certain conditions, which are not yet sufficiently explained to exist a long time in water and transport with it diseases from place to place. Particu-larly the spread of cholera observed in many epidemics of that disease along the water course of rivers has been connec-ted with a transportation of the cholera germ through the water.
§ 46. Artificial purification of the surface water. Filters.
II. Water. 49
According to ihe foregoing observations the use of surfac water for drinking or domestic purposes must be considered hazar-dous; but by certain processes one succeeds to remove more or less the noxious qualities of such water.
The surest way of destroying the germs of disease in water is by thorough boiling it, but the water then loses its carbonic acid and with the latter its refreshing taste. Most
Fig. 21.
Filtt·r :-.i licion mal'l acco1-diu~
to llcl'k<'feld.
chemical means used for purifying water arc less successful in killing the germs of disease ; moreover the water also loses thereby its taste.
Those processes, based upon the fact, that one allows the water to deposit its impurities by being kept standing for a longer period of time in clarifying vessels, only remove the coarser impurities, and therefore are insufficient. Filters however are of greater value. Small filters, so-called house filters (Fig. 20),
4
in the construction of which charcoal, asbestos, porous stones, burnt clay, porcelain or silicious marl (Fig. 21) are employed, can clarify the water very well, but they cannot reliably free it, and then at most only temporarily from the germs, which it contains. For as a growth of microbes takes place in the sides of the filter, the germs, contained in the filtered water increase in a short time, and may be finally more numerous, than before filtration.
More successful are the sand filters (Fig. 22), which are used in many towns for purifying water. These sand-filter
Fig. 22. Plan of a large sandfilter for purifying surface-water.
beds extend over large surfaces, on which are laid in layers, first on the bottous flat stones, then smaller stones, then gravel, lastly fine sand on top. The water, to be purified, filters through all these layers from the top downwards, passes then through canals into pure water reservoirs and from these into the pipes and the water tanks. As the real filtering part of the bed must first be deposited in the form of a fine mud-coating on the surface, the first water, coming from a newly-erected or cleaned filter-bed is allowed to run off waste.
When properly built and conscientiously worked the sand-filters retain the coarser impurities of the water completely, and also the bacteria to a great extent; but when improperly constructed or with want of care in their use the results of filtration may be completely lost. Hence in the German
II. Water. 51
Empire strict government supervision is required in the con·
struction and use of sand filters which are built for the puri-fication of surface water. Many experts however desire, that, whenever possible, deep underground or deep well-water should be exclusively used for drinking water arrangements, and surface-water should be entirely disregarded.
§ 47. Sea-water. The kind of surface-water, most widely spread over the earth is the water of the oceans, the sea-water. This is unfit for drinking on account of the high percentage of salt, it contains. If however it is necessary to use it as drinking water, it must be distilled i. e. boiled, and the ascending steam conducted through a cool tube. By this process the steam is again condensed into water and the salts remain behind in the kettle. Such water however is only drunk in case of necessity and with some admixtures, as without such additions the water, owing to its want of gaseous and mineral ingredients has an insipid taste and cannot be well digested.
§ 48. Mineral water. On its way through the soil (§ 43) water has sometimes an opportunity to take up certain mineral ingredients, especially salt and gaseous substances in large quantities; these ingredients give to the water salubrious qualities. Such water is called mineral water. Many kinds of mineral water, which are refreshing beverages are highly esteem-ed by many healthy and sick persons; these (such as selters-water, containing a large quantity of carbonic acid) are arti·
ficially imitated to a large extent by forcing carbonic acid into ordinary water under strong pressure. These imitations may be injurious to health, if bad water is employed in their preparation.
§ 49. Use of water in removing dirt. The importance of water for our health is not exhausted by its use as drinking water; on the contrary; of the water, consumed by us, which on the average varies from 50 to 150 litres per day for each individual according to the mode of his life, only three to four litres is used for domestic purposes, inclusive of the portion, indispensably necessary for the preparation of food.
The remainder is meant for purposes of cleanliness and for the removal of dirt.
All elements of dirt, which are found in our surroundings or adhere to our body, our linen, our clothing can become
4*
in,iurious to our health. As together with earthy matter, they always contain the refuse of the organic world i. e.
remains of animals and plants, they usually pass very easily into a state of decomposition and become offensive to us by their smell. Besides, they also sometimes contain the pul-verized elements of dried-up expectoration and other excreta of sick persons, which may include germs of disease. Such dirt easily contaminates our food, or when whirled about as dust penetrates through our digestive or respiratory organs into the body ( cf. § 182). The surface of our body also affords to these elements of dirt a field for their injurious effects, for they penetrate through the pores into the small glands or through small wounds pass under the skin, mingle with the secretions of the skin-glands and thus find their way into the interior of the body. ln this way is explained the origin of many diseases of the skin, which appear sometimes as eruptions or small superficial sores, sometimes however, when specially dangerous germs adhere to the dirt-elements cause erysipelas, inflammation, or festering of the cell-tissues (cf. § 215-217).
:B'or the removing of dirt water offers us the best means.
We sprinkle the streets with it, we cleanse our dwellings and make use of it for the washing of our clothes, numerous domestic utensils and of our body. In these cases it is also not a matter of indifference, what class of water is used. As cleansing not merely consists in a washing away of the dirt, but is assisted also by the capacity of the water for dissolving other substances, the process succeeds best when soft water is used.
For cleaning of our body and of our clothes rain water, and failing it, surface water is particularly esteemed. It ought not to be forgotten however, that contaminated surface-water, i. e. water from sources, which receives outflows from house-or public drains, house-or which has been used fhouse-or washing clothes of sick persons, may produce sicknesses in persons, who imprudently come in contact with it. In cases, where, through Jack of soft water, recourse must be had to hard water, it is advisable to boil it before using it, because thereby a part of the mineral substances, causing the hardness is separated and the capacity of the water for dissolving dirt elements is increased.
§ 50. Auxiliaries of water for cleansing. Cleansing of