48 ILLINOIS ACADEMY OF SCIENCE 



Purity of Well Waters. 



Showing Percentage of Well Water Condemned x\nnnally by 



the Water Survey. Arranged According to Depth of 

 Well. 



1907 1908 1909 1910 1911 1912 Total 



Less than Twenty-five ft.— 



No. Examined 284 254 242 148 113 168 1209 



Xo. Condemned 240 192 183 118 74 113 920 



Per Cent Condemned 85 75 75 79 65 67 76 



Twenty-five to Fifty ft. — - 



Xo. Examined 224 395 354 201 196 353 1723 



Xo- Condemned 173 250 226 137 122 185 1093 



Per Cent Condemned 17 63 63 65 62 52 63 



Fifty to (^ne Hundred ft. — 



Xo. Examined 111 192 161 90 89 129 "HI 



Xo. Condemned 42 66 54 46 8 28 244 



Per Cent Condemned 17 34 't^I 51 9 22 32 



Over One Hundred ft. — 



Xo. Examined 161 312 376 205 171 339 1564 



Xo. Condemned 22 31 62 43 30 49 237 



Per Cent Condemned 13 9 16 20 17 14 15 



Unknown Depth — 



No. Examined 88 46 72 67 19 27 319 



Xo. Condemned 34 22 38 35 9 6 U4 



Per Cent Condemned 38 47 52 52 47 22 45 



Total Xo. Examined 868 1199 1205 711 588 1016 5587 



Total Xo. Condemned 511 561 563 379 243 381 2638 



Per Cent Condemned 60 46 47 53 41 38 47 



average number condemned decreases with the depth of the 

 well. Of those less than 25 feet in depth 76 per cent werq 

 condemned, of those 25 to 50 feet, 63 per cent were condemned, 

 of those 50 feet to 100 feet, 32 per cent were condemned, 

 of those 100 feet in depth only 15 per cent were con- 

 demned and many of the deepest were condemned because 

 of excess of mineral content and not because of con 

 tamination. Of those of unknown origin 45 per cent 

 were condemned. Of all the well waters received 

 during the six years, 47 per cent were condemned. It 

 is gratifying to note a decrease in typhoid fever during the 

 latter part of the period. 



W^ithout doubt the above does not give the true idea of 

 the actual condition of the water obtained from wells through- 

 out the state. As a matter of fact a majority of samples sent 

 to the W^ater Survey for examination is sent because of 

 typhoid fever among those using the water. A truer estimate 



