Whenever Emile is thirsty let him have a drink, and let him drink fresh water just as it is, not even taking the chill off it in the depths of winter and when he is bathed in perspiration. The only precaution I advise is to take care what sort of water you give him. If the water comes from a river, give it him just as it is; if it is spring-water let it stand a little exposed to the air before he drinks it. In warm weather rivers are warm; it is not so with springs, whose water has not been in contact with the air. You must wait till the temperature of the water is the same as that of the air. In winter, on the other hand, spring water is safer than river water. It is, however, unusual and unnatural to perspire greatly in winter, especially in the open air, for the cold air constantly strikes the skin and drives the perspiration inwards, and prevents the pores opening enough to give it passage. Now I do not intend Emile to take his exercise by the fireside in winter, but in the open air and among the ice. If he only gets warm with making and throwing snowballs, let him drink when he is thirsty, and go on with his game after drinking, and you need not be afraid of any ill effects. And if any other exercise makes him perspire let him drink cold water even in winter provided he is thirsty. Only take care to take him to get the water some little distance away. In such cold as I am supposing, he would have cooled down sufficiently when he got there to be able to drink without danger. Above all, take care to conceal these precautions from him. I would rather he were ill now and then, than always thinking about his health.