GENERAL SUGGESTIONS r. Devote the first lessons to swimming drills on land, and continue until the pupils are ready for water practice. The lessons should be varied by the addition of the rescue, release and resuscitation drills.' All these exercises can be taught in the schoolrooms.
2. For the lesson in the water, the pupils should take up position in line, hold a rail or other support, and by word of command immerse themselves completely 3. Several lessons should be devoted to practice in floating. In this exercise the pupils should support each other. To ensure success care should be taken to keep the surface of the water as calm as possible.
4. For the practice of the leg stroke the pupils should grasp the rail with the left hand, and place the right hand on the wall of the bath, about fourteen inches below the left, and extend the body full length on the surface ; when ready, repeat the leg drill.
5. For the combined movement of the arms and legs the pupils should be ranged at the side of the bath, and work in pairs, by supporting each other alternately in swimming across the bath. Continue the lessons until the pupils are able to swim, when diving must be taught, and regular practice taken in distance and back swimming.
It is impossible to formulate—or, indeed, clearly to under stand—the theory which should regulate all attempts to teach swimming without some knowledge of the natural laws, espe cially of the law of specific gravity, which govern this method of progression.
Specific gravity is the ratio of the weight of a body to the weight of an equal bulk of some other body taken as the stan- dard or unit. In the case of solids, the standard is usually water. The specific gravity of a healthy person is made up of the combined specific gravities of the various parts of the body, and is therefore a complex quantity. The only portion of the body which is lighter than water is fat, its specific gravity being • according to Arnott o•92 ; and it has been calculated that the proportion of fatty matter in an adult is 5 per cent., or
twentieth part of the weight of the body. The stated specific gravities of the other portions of the body are as follows :— muscle 1.o85, brain ro4, soft organs generally ros, lungs (containing air) 0•94, bone, the heaviest part of the body, The lightness of the fatty portion is, therefore, more than counterbalanced by the weight of the bones (about ten and a half pounds in the male, and nine pounds in the female), so that if a human body be placed in the water it has a slight tendency to sink. This tendency decreases in proportion to the quantity of the body immersed, because all those parts which are out of the water, not being supported by water, become so much additional weight to the portion immersed.
An inexperienced person exhausts himself by quick action and the raising of the body continually out of the water; for as soon as the hands or any part of the body are uplifted the tendency is to sink, owing to the fact that the part raised out of the water at once acts as if a weight had been applied to sink the person. When the whole of the body is immersed, and the chest fully expanded and inflated, the specific gravity differs so little from that of water that if a person turns on the back, places the hands beyond the head at full stretch in a straight line with the body, and also inclines the head well back, this will suffice to keep him on the surface ; but, as a rule, continual practice is required. Several writers have argued that it is natural for man to swim, because it is possible to float with ease when turned on the back with the lungs in flated. A person suddenly immersed cannot get into this position, but struggles and splashes, brings the hands forward, and consequently the head as well. Owing to the weight of the bones of the skull, the head has a great tendency to sink below the level of the water, so that when brought forward muscular force is required to keep it above.