eo ters . 

AMERICAN MUSEUM’ OF NATURAL HISTORY 
SYLLABUS GUIDE 
TO THE PUBLIC HEALTH EXHIBITS 
WATER SUPPLY 
Most of the water on the earth’s 
surface is stored in the oceans, from 
which it is drawn up or evaporated by the 
sun to form the clouds. 
The rain is the primary source of all 
water supplies. Rainfall varies consider- 
ably at different places. 
Surface water flows off in rivers— 
which are swift at first, but slow and 
winding farther down. 
Slowly flowing rivers, unless con- 
taminated by sewage from towns on their 
banks, are less apt to be dangerous than 
rapid ones, but safer than either are lakes 
in which the water is stored—undergoing 
through storage a natural purification. 
A common way of obtaining water 
supplies for large cities is by impounding 
streams in artificial lakes and reservoirs. 
Another portion of the rain sinks at 
once into the ground, often to emerge 
at a lower level, forming a spring or 
well, — another common source of public 
water supply. 
Water may be hard or soft, turbid 
or clear, depending upon the amount and 
nature of the matter which it contains in 
solution or in suspension. 
Drinking water frequently contains 
microscopic organisms, most of which are 
harmless, although some of them produce 
tastes and odors in the water. 
(Nores REFERRING TO 
ExuHrpits) 
See 1st panel of frieze, left wall. 
WALL CASE 1 shows the number 
of rainy days at certain places and the 
actual rainfall in inches at others. 
WALL CASE 2 presents graphically 
rainfall dataforthe whole United States. 
See 3d panel of frieze. 
See 4th panel of frieze. 
See 2d panel of frieze. 
Jars of rice in WALL CASE 3 indicate 
how typhoid bacilli die off during 
storage but CHART 1 shows a case 
where purification by storage failed. 
- 
CENTER CASE 1 shows how a 
reservoir was formed near Boston, 
Massachusetts, for this purpose. 
In WALL CASE 4 is a section of an 
artesian well. 
The physical character of five samples 
of water is indicated by blocks in 
WALL CASE 3. 
In WALL CASE 3 are displayed en- 
larged glass models of micro-organisms 
(algae, diatoms and protozoa) which 
occur in water. 
Their seasonal prevalance is shown by 
CHARTS 2 and 3. 
