204 THE MONTESSORI METHOD
noteworthy way to practical discipline. We all know how the younger children disturb the order of the room by shouts, and by the noise of over-turned objects.
The rigorous scientific education of the sense of hearing is not practically applicable to the didactic method. This is true because the child cannot exercise himself through his own activity as he does for the other senses. Only one child at a time can work with any instrument producing the gradation of sounds. In other words, absolute silence is necessary for the discrimination of sounds.
Signorina Maccheroni, Directress, first of the " Children's House " in Milan and later in the one in Franciscan Convent at Eome, has invented and has had manufactured a series of thirteen bells hung upon a wooden frame. These bells are to all appearances, identical, but the vibrations brought about by a blow of a hammer produce the following thirteen notes:
The set consists of a double series of thirteen bells and there are four hammers. Having struck one of the bells in the first series, the child must find the corresponding sound in the second. This exercise presents grave difficulty, as the child does not know how to strike each time with the same force, and therefore produces sounds which vary in intensity. Even when the teacher strikes the bells, the children have difficulty in distinguishing between sounds. So we do not feel that this instrument in its present form is entirely practical.
For the discrimination of sounds, we use Pizzoli's series of little whistles. For the gradation of noises, we use