NATURAL AND PHYSICAL SCIENCE, 1700-1800 311 



upon the ear-drum, and in one of his dialogues explains concord 

 and dissonance by concurrence or conflict of such vibrations. 

 He shows how vibrations causing sound may be made visible, and 

 how to measure the relative length of sound waves by scraping 

 a brass plate with a chisel, thereby making dust on the plate take 

 up positions in parallel lines. That air is really the intermediary 

 was proved in 1705 by Hawksbee's experiment of placing a clock 

 in a vacuum. 



After Galileo, the studies, mathematical and experimental, of 

 Newton, Euler, and Sauveur (1653-1715) brought acoustics to 

 the point where it was taken up and given much of its present 

 form by Chladni (1756-1827) "the Father of Modern Acous- 

 tics." Sauveur, eminent physicist and musician, deserves more 

 than passing notice from the fact that he "had neither voice nor 

 ear" (being half deaf and dumb) and yet achieved distinction for 

 his original researches in both sound and music. Intended by his 

 parents for the church, he early manifested delight in mechanical 

 contrivances and in arithmetic, but the course of his life was 

 determined by a copy of Euclid which accidentally came to his 

 notice. He thereupon abandoned an ecclesiastical career and, 

 having in consequence lost the support of his relatives, obtained a 

 livelihood by teaching mathematics, becoming a professor of 

 that subject in 1686. During the remainder of his life the study 

 of acoustics, and particularly the scientific theory of music (in 

 which he was the first to draw attention to overtones or har- 

 monics) occupied much of his attention. Many of his papers 

 were published in the Memoirs of the French Academy, 1700-1714. 

 The work of Chladni at the beginning of the nineteenth century 

 laid broad and deep the foundations of acoustics as we know that 

 science to-day, and upon this foundation Helmholtz and Tyndall 

 in the middle of that century reared a large part of the modern 

 superstructure. Chladni carried much further the experiments of 

 Galileo on vibrating plates, substituting a violin bow for the 

 chisel, and sand for dust on the plates, obtaining thereby that 

 wonderful variety of figures which is nowadays demonstrated 

 to beginners by every teacher of natural philosophy. He also 



