_The Common Gases_ dissolved or imprisoned by well and spring water are carbonic acid, sulpurretted hydrogen and the components of air—oxygen and nitrogen. Of these only one is dangerous—sulpurretted hydrogen—and that is easily detected by its smell, resembling that of spoiled eggs. It gives the characteristic odor to “sulphur” waters. Carbonic acid and air give to waters their sparkling quality—the former being often artificially introduced, as in “soda-water,” &c. _The Organic Matter_ in well, spring, and river water may be dead or living, and we will consider the two classes separately. Lifeless Organic Substances.—These may be the remains of organized bodies and plants once living in the water, or animal and vegetable matter from some outside source. The latter is the most frequent source of organic impurity. In localities where heat and marshes abound, water may often be colored by organic acids and other substances which dissolves, and yet not be appreciably unhealthy. Such waters are common in some countries, and present dangerous _possibilities_, should fermentation and putrefaction at any time set in. Decaying fish and animals, leaves, &c., &c., form the ordinary and accidental organic impurities of water. These are unhealthy not only in themselves, but especially because they offer to the germs of disease or pestilence a harbor and sustenance. As was stated in the early part of the paper, men must be protected from themselves and especially against water of their own poisoning. Nature’s strivings are constantly to make clean the unclean; to dissipate the noxious and to destroy the hurtful, but man by breaking nature’s laws, brings ten fold vengeance on his head. The most dangerous poisons in well water are the drainings of sewers, sinks, yards and privies, and the refuse from towns. These organic, poisonous matters ooze through the soil into wells and springs, and as before said, _may_ not show any bad effect for sometime, but sooner or later disease and death will surely visit the unsuspecting household and the physician’s aid be sought in vain, for with every draught of water which passes the fevered lips, the sufferer imbibes new poison and hastens the inevitable end. Moreover, the germs of many contagious diseases, which feed on filth and multiply in foul water, are nurtured and preserved in warm climates through winter weather, by the equable temperature of wells and cisterns, and are ready to start anew on their errand of death, when a favorable moment arrives. The city of Wilmington is no doubt above the general average of Southern cities in sanitary condition, but what a picture the February number of the JOURNAL showed us. Think of it! “_There was one well two feet from the privy, two wells four feet from the privy, thirty-three wells ten feet from the privy, two hundred and twenty wells from twenty to thirty feet!_”