PREFACE.

THE books of the "Experimental Science Series for Beginners" originated in the earnest and honest desire to extend a knowledge of the art of experimenting, and to create a love of that noble art, which has worked so much good in our generation.

These books, though written for all those who love experiments, and wish to know how to make them with cheap and simple apparatus, will, it is hoped, be found useful to teachers, and especially to the teachers and students in our Normal Schools. The majority of those who go from these schools will be called to positions where only a small amount of money can be obtained for the purchase of the apparatus needed in teaching science. These little books will show how many really excellent experiments may be made with the outlay of a few dollars, a little mechanical skill, and-patience. This last commodity neither I nor the school can furnish. The teacher is called on to supply this, and to give it as his share in the work of bringing the teaching of experimental science into our schools.

When the teacher has once obtained the mastery over the experiments he will never after be willing to teach without them; for, as an honest teacher, he will know that he cannot teach without them.

Well-made experiments, the teacher's clear and simple language describing them, and a free use of the blackboard, on which are written the facts and laws which the experiments show-these make the best text-books for beginners in experimental science.

Teach the pupil to read Nature in the language of experiment. Instruct him to guide with thoughtfulness the work of his hand, and with attention to receive the teachings of his eyes and ears. Books are well-they are indispensable in the study of principles, generalizations, and mathematical deductions made from laws established by experiment-but, "Ce n'est pas assez de savoir les principes, il faut savoir MANIPULER.”

Youths soon become enamored of work in which their own hands cause the various actions of Nature to appear before them, and they find a new delight in a kind of study in which they receive instruction through the doings of their hands instead of through the reading of books.

The object of this second book of the series is to show how to make a connected series of experiments in Sound. These experiments are to be made with the cheapest and simplest apparatus that the author has been able to devise. I have tried to be plain in giving directions for the con