through sand and charcoal. The necessity, however, for frequently cleaning the charcoal should not be forgotten.
The quantity of water needed to maintain the proper condition depends very greatly upon the individual and upon the temperature. In very warm weather considerable water is necessary, that the exterior part of the body may be cooled by evaporation, or perspiration, as it is usually termed. No matter how high the atmospheric temperature, the body retains in all cases when in a normal condition, a temperature of about 98½ degrees Fahrenheit, and this is maintained simply by the cooling of the exterior surface from evaporation; thus you can readily see, if engaged in some vigorous exercise that heats the blood, or if the temperature is high, the necessity for water greatly increases.
Though pure water is unquestionably of great advantage, it would be well to call attention to the fact that if the body is in a normal condition of vigorous health there is little danger from water which gives no evidence of im-
