INVESTIGATION OF DRINKING WATER SUPPLIES 165 
in the hands of an untrained observer who is often incompetent 
to undertake the work. This same unskilled individual is 
entrusted with the duty of securing samples of water that 
must be properly collected if satisfactory results are to be 
obtained. These samples are then shipped to the laboratory 
and subjected to a most careful examination by a skilled 
technician when there is little assurance of the accuracy of 
their collection. This method makes it necessary for the skilled 
worker to accept facts from an untrained person on the funda- 
mental features of an investigation on which the safety of 
a water supply is to be judged. The fallacy and danger of 
such practice is very evident when these points are considered. 
The importance of thorough investigation work on water 
supplies is illustrated in the following tables. These tables 
include six years of investigation work on existing water sup- 
plies by the Minnesota State Board of Health. 
TABLE I.-WATER SUPPLY INVESTIGATIONS, 1912-1918 
| Results 
Water Supplies Investigated 
Satisfactory | Unsatisfactory 
Number ssus6ss0)sjeiainserianeiaesncicrelawens laleeges 1,119 389 730 
Per cent ......... sears uy aa apes 100 34 66 
The investigations recorded in Table I represent both sur- 
face and underground water supplies from a variety of 
sources including wells (dug, bored, drilled, driven), springs, 
lakes, rivers, creeks, etc. This table shows that 1,119 existing 
water supplies were investigated during the period indicated. 
Three hundred eighty-nine, or 34 per cent, were shown to 
he safe and 730, or 66 per cent, were found to be unsafe 
sources in their existing condition. 
TABLE IL—UNSATISFACVrORY WATER SUPPLIES, 1912-1918 
Shown Unsatisfactory by 
Unsatisfactory Water 
Supplies Field survey and Field survey Analytical results 
analytical results 
Number ...... .......6+ 730 354 | 338 | 38 
Per cent ........0.0-e05 160 49 46 
