The efficiency of different materials of which clothing is made also depends upon their capacity to absorb water. This may be done in two ways: the water may simply collect between the fibers, in which case it may be in a large measure removed by wringing, or it may be actually absorbed into the substance composing the fabric, and, as a consequence, the latter, even though containing much moisture, do not appear damp. Fabrics made from vegetable materials, as cotton or linen, have little power of actually absorbing water, and hence they become wet on the slightest addition of moisture, while on the other hand those of animal origin have the capacity of absorbing water, and appear dry even after the addition of this substance in considerable amounts. A person, therefore, dressed in cotton fabrics will find after active perspiration has begun that his clothing quickly becomes moist, while if he have on woolen garments this will not occur. It is particularly noteworthy that water is gradually removed by evaporation from animal fabrics, which causes a general cooling without producing a chill; it is therefore readily understood that woolen clothing is much to be preferred where active exercise is being taken. Color is also of some importance in determining the value of a fabric for protecting the body from the sun's heat. Within recent times we have learned a great deal respecting the wonderful penetrating power of the invisible light rays, and we have every reason to believe that these modify to a very considerable degree every process going on within the body. The violet and ultra-violet rays are those that unquestionably exert most influence, and it has been suggested that they may be broken up and rendered innocuous by covering the body with materials having a reddish-yellow color. It is not necessary to put these materials on the outside where they would be conspicuous, but they may be used as lining for hats and clothing; and there are good reasons to believe that if their use were generally adopted suffering and actual loss of life from overheating would be greatly reduced, particularly in warm countries. _Work and Rest._--Very slowly the people of our country are beginning to realize that it is quite as necessary to rest as to work, though unfortunately in some quarters a strenuous life is urged as being only secondary in importance to possessing a big family; that there is an intimate association between the two there can be no doubt, since the latter beyond peradventure would entail the former. It has ever been the habit and misfortune of sages now and then to desert the field of their own peculiar activities and to make incursions into unknown regions--generally giving advice with a dogmatism and finality proportionate to their ignorance of the subject under discussion.