The color of underclothing has practically but little influence upon the amount of heat radiated from the body, but the color of the outer dress has much to do with regard to the amount of heat absorbed from the sun’s rays. =Absorption of Moisture.=--The property of absorbing moisture is of much importance in the hygiene of clothing. The best material for clothing to be worn next to the skin is that which, while retaining the natural heat, or giving it off very slowly, absorbs the moisture from the body, and diffuses it through its meshes. The skin is thus relieved of the cooling effect of this evaporation, which might prove harmful. =Porosity.=--The ventilating property of clothing, or the ease with which air passes through its meshes, is called porosity. The most porous of dress fabrics is flannel, which is, at the same time, the warmest. Its porosity, as compared with that of linen, is as 100 to 58. =Impermeability to Water.=--As a protection against rain, the simple mackintosh, or the mackintosh cloth, is the best. The latter is more pleasing to the eye, but the outer wool covering absorbs enough moisture to add somewhat to the weight of the garment, which is a slight disadvantage. All waterproofs present this serious evil, that while they exclude the outer moisture, they prevent the escape of the natural moisture from the surface of the body. This, however, is, generally speaking, a lesser evil than to expose the body to storm and cold, with the risk of serious illness. It is not unusual to add to the waterproof the further protection of an umbrella. In such case, the discomfort of excessive perspiration may be relieved by occasionally loosening a button or two about the neck and chest. =Underclothing.=--Taking all things into consideration, wool is, without doubt, the best material for garments worn next to the skin. In cold weather it maintains the natural heat of the body. In warm weather it quickly absorbs the free perspiration, giving off the moisture through its meshes, and thus preventing the too rapid evaporation from the surface of the body, which tends to produce chill and other resulting disorders. It also serves to protect the body from the hot rays of the sun, and from the heat of boilers and furnaces. No other substance so effectually modifies the evil effects of sudden and rapid changes of temperature. In the extreme cold of the polar regions and in the oppressive heat of the tropics, it is alike satisfactory. The thickness of the texture and the closeness of the weave must be determined by the climate and the season.