CHEMISTRY AND PHYSICS. 59 
some cases the odor accompanying their growth renders the water quite objec- 
tionable, and neither natural nor artificial filtration is able to remove it. 
‘* Hither natural or artificial basins may have a collection of vegetable matter 
on the bottom, which slowly decomposes in summer, and, since the bottom water 
is colder, the resulting ammonia remains till the late fall overturn, when it is 
brought to the surface, where it favors the growth of diatoms and other cold- 
water plants. Certain diatoms, as asterionella, cause disagreeable odors. Such 
basins show the least ammonia in early October and the most in late November. 
‘Tn order to make any predictions as to the probable development of this flora 
and fauna of water, experience and at least a year’s watching of any given sup- 
ply are required, until more is known of the life-history of these forms of life. 
Nothing is more needed to-day than work along these lines. When may disagree- 
able tastes and odors be expected? What precaution or measures may be taken 
in each case to prevent them? These are the questions the water-works superin- 
tendent, equally with the consumer, is asking, for the most part vainly, as yet.”’ 
In some of the Eastern states these algee have caused much trouble, especially 
where water is stored in ponds and small lakes. In our own state there has been 
some little trouble with tastes and odors, probably due to this cause, where a 
supply is obtained from a small stream, and, as the state becomes more densely 
populated and more water plants are built, many of which will be forced to col- 
lect and store the water, this is quite likely to increase. 
At the present time in Kansas most of our water-works Biante secure their 
supply from ground-water. This comes from that part of the rainfall, some 
twenty-five to forty per cent., that soaks into the soil and becomes partially or 
nearly purified by its action. This percolates more or less slowly downward, ac- 
cordingly as the soil is close or open in texture, until it is stopped by some imper- 
vious stratum; then it flows in a sheet in the strata immediately above, which 
are completely saturated. This motion is a slow one, varying from only a few 
inches a day in close, clayey soils, to several feet in the open, sandy or gravelly 
layers, and is one of continuous progression. This sheet-water does not generally 
lie very deep and is constantly seeking an outlet, where it appears in the shape 
of springs, or breaks out beneath the beds of rivers or smaller streams. This 
movement of the underground water is too little realized by the average man who 
digs a well, and thinks, because the water derived is clear and cool, that it is a safe 
one for his use. The fact is, that even the isolated well of a farmer’s home may 
harbor much of evil, while town wells asa whole are often much more dangerous 
than the public supply which may be furnishing a water less palatable or pleas- 
ing in appearance. The reasons therefor are not far to seek. 
In the soil, which is acting as a filter for the purification of the water that 
passes through it, much the same agencies are at work in performing the task as 
were found accompanying the changes in surface-waters. In its top layers, 
chiefly within the upper twelve inches and rarely extending any deeper than 
three or four feet, are found the nitrifying bacteria, different in species perhaps 
from those at work in the adjacent streams, but yet with similar life-histories 
and producing similar results. In the shape of nitrates they return the nitrogen 
to the soil, where it can be taken up again by the tiny rootlets of growing plants. 
If these organisms have time to do their work, if the conditions of temperature, 
supply of oxygen, etc., are adapted to their need, then the water of the lower 
layers is freed from its organic nitrogen. An analysis of well-water then shows 
very little albuminoid or free ammonia and probably no nitrites, while all of the 
suspended matters that give cloudiness or turbidity to the water have been 
strained out and left behind in the interstices of the soil. On the other hand, if 
