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coffee, beer, or wine, but the necessity of taking a portion of the water we daily consume as pure as it can be had.

Now there are many sources of water. The first great source is the ocean, which collects all the water from the earth; and this water contains so large a quantity of salt, that none of us can drink it. The shining sun, however, bears down upon the ocean's surface, and its heating rays penetrating the water, combine, as it were, with it, and raise it up. The atmosphere, like a sponge, absorbs the vaporous water, carrying it from the Equator to the Arctic and the Antarctic regions; thus distributing it north and south. It then condenses in the form of rain and of snow, when, sinking into the earth and pouring down its mountainsides, it forms springs and rivulets, entering the ocean again in the form of rivers; and now man catches it in tubs or cisterns, in its progress in the rivers, or digs down into the earth, and catches it as it passes along beneath his feet. Thus we have rain-water, river-water, and spring or well-water.

I need not dwell on sea-water; but it is a very interesting fact to know, that by a process invented by my ingenious friend Dr. Normandy, sea-water may be distilled and rendered perfectly pure and fit for human use.

With regard to rain-water, there is no doubt that it is one of the purest waters that we have, arising from the fact that it is the first condensed water after it has passed from the ocean into the atmosphere; but its use is liable to the objection, that, where it runs down the sides of houses into cisterns, it passes through an atmosphere frequently contaminated with sulphurous

acid and ammonia; and the unconsumed carbon of chimneys, of which we have so constantly unpleasant reminders in large towns. Still, where rain-water can be collected in the open country, there is no doubt that it is the purest form of water. It is, however, on spring and river-water that we are more dependent; and to the spring and well-waters I would more especially call your attention.

There are two kinds of well-waters, or springwaters, which are consumed in London, as well as most other parts of the world; and those are the surfacewell waters and the deep-well waters. In London, we dig down deep into the chalk and get water from below the London clay; this is deep-well water. If you glance at this diagram (Fig. 2), you will see how this is.

[graphic][merged small][merged small][merged small]

Here we have represented a section of the valley in which London is situated: it is formed in the chalk. London is, in fact, situated in a basin of chalk. Above the chalk is a deposit, varying in thickness, branching off to the side of the basin, as you see of London clay; above this clay is a layer of gravel. Now the water passing through or under this gravel, gradually accumulates on the clay; so that if you dig 20 feet or 25 feet in any of the gravelly districts of London, you get

plenty of water; this is called surface-well water; but, if you want to get pure water, you must dig deeper than the clay; you must go through the clay down to the chalk. Wells dug down to the chalk are called Artesian wells. I shall have to speak of these waters again when I speak of the constituents of water; but I may just say here, that persons suppose it is a matter of indifference whether they obtain their water from surface-wells or from deep wells. This, however, is not the fact; for, although surface-well water is frequently clearer, cooler, and more sparkling than deep - well water, it is always liable to suspicion. The sparkling of these waters arises from the carbonic acid gas they contain; and in nine cases out of ten that carbonic acid is derived from the decomposition of animal and vegetable matters. Their cooling taste is no less indicative of their impure origin, as it arises from the formation of salts, which could only occur from the decomposition of organic matter.

The situation of these wells, especially in London, explains the origin of these impure matters. The water that supplies the surface-wells of London is derived from the rain which falls upon the surface of the land, and which percolates through the gravel, and accumulates upon the clay. Now this gravel contains all the soakage of London filth; through it run all the drains and sewers of London, and its whole surface is riddled with innumerable cesspools. Here is the source of the organic matter of surface-well waters, and also the cause of their coolness, their sparkling, and their popularity. In most small towns there is a public pump, and, when this is near the churchyard, it

is said to be always popular. The character of the water is no doubt owing to the same causes as that of London surface-wells, the remains of humanity in the churchyard supply the nitrates and carbonic acid of the

water.

From this kind of impurity the water of deep wells in London, and of wells cut into rocks which bring their water from a distance from towns, are entirely free. They frequently contain inorganic salts in abundance, but they do not contain organic matters; hence, for drinking purposes, they are very preferable to the waters of surface-wells. A great number of these wells exist in London. There is one attached to almost every brewery in London, and other manufacturers, who need pure water for their operations, sink these wells.

If you require ocular demonstration of the impurity of surface-well water, let me draw your attention to a series of these waters in the South Kensington Museum, where you will observe that the effect of time and exposure upon the surface-well water has been to organize their dissolved organic matters, and the bottles exhibit a variety of forms of plants which have been thus developed.

Then we come to river-water. The great distinguishing feature of river-water is, that, being exposed to the air, it becomes the medium of life to both plants and animals. We have not only fish, and snails, and reeds and pond-weeds growing in river water, but we have innumerable forms of microscopic animals and plants. Even after this water is filtered, and supplied to towns, as in the case of the Thames to London, these microscopic creations abound. Here we have a drawing,

[graphic][subsumed]

Fig. 3.-Water from Grand Junction Company (from Cistern).

a. Paramacia, 2 species.

b. Vorticella convallaria.

c. Coleps hirtus.

d. Pandorina Morum.

e. Scenedesmus quadricauda.
f. Navicula amphisbæna.
g.
sphærophora.

h. Asterionella formosa.

i. Fragilaria capucina.
k. Brown active sporules.

1. Stationary Green sporules.
m. Threads of slender Fungus.
n. Organic and Earthy Matter.

copied from one published by Dr. Hassall, representing some of the interesting microscopical objects which are supplied in the river-water. The filtration is improved since this drawing was made, but there is still enough of them supplied to render the Thames water, as sup

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