Page:Popular Science Monthly Volume 35.djvu/266

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the bottom of the well and in the mud there. It is especially this mud that must be regarded as the native soil of the different organisms which are to be referred to in the following article; and this at once forcibly calls to our attention the fact that turbid well-water (that is, water which may be suspected of holding mud-particles in suspension) should under no circumstances be used for drinking purposes. Water, clear and sparkling, from a mountain brook, or water drawn from a good well, will, even under a microscope, present nothing that could arouse the aversion of the drinker, or raise doubts as to its desirability from a sanitary point of view.

It is but of late that the attention of naturalists, and especially of zoölogists, has been drawn to the peculiar kinds of animal life which exist in the depths of wells. Credit is due chiefly to Prof. Franz Vejdovsky, in Prague, for calling the attention of scientists to this realm of the animal world. Already many years ago the searching eye of Science had penetrated to the greatest depths of the oceans and inland seas; untiring zeal had discovered interesting phases of animal and plant life in dark caves and grottoes, as well as on the snow-fields of the Alps. But the wells had thus far been left unsearched, and here there still remained a wide field for the explorer, for the making of interesting observations and discoveries.

A peculiar circumstance led to a systematic examination of wells in search for the organisms they might contain. The death rate at Prague had grown to be very high, and this created in the mind of the public the idea that the condition of the water supply there was at fault. In 1879 a committee was appointed which was to make a practical investigation into this matter. At the request of this committee, Prof. Vejdovsky has, in a period extending over two years, examined with the microscope the water of more than two hundred wells of the city of Prague, in order to study the noxious organisms suspected of existing therein.

Of course, it is only possible to acquire knowledge of this kind by obtaining a sufficient quantity of mud from the well which is to be examined. This is done by sinking an apparatus especially constructed for the purpose into the well-shaft. The scoop consists of a stirrup made of iron, a foot and a half long and half a foot broad, to which a bag of coarse canvas is attached. This contrivance is fastened to a rope from twenty to thirty metres in length, and, in order that it should sink deep into the mud, a cannon-ball, weighing from eight to ten pounds, is fastened to it at the proper place.

According to the kind of well, the canvas bag is either dragged over the bottom, so that it may gather up the mud, or the rope is jerked up and down; the water is thus stirred up and rendered