Page:Popular Science Monthly Volume 38.djvu/870

850 side and back to the point of rest. Regular and continuous vibrations produce music; irregular vibrations result in noise. There are four laws or canons of the stretched string, depending upon its length, thickness, tension, and density. Vibrations become audible when they reach the rate of sixteen per second and vanish at the point of 38,000 per second. Overtones are likened to the wavelet3 which form part of a larger ocean wave. The sound-waves, however, divide with mathematical regularity, and the laws concerning them were first formulated by Helmholtz in 1863. The number and strength of overtones, or harmonics, cause us to recognize the difference between two instruments, as flute and violin, when sounding the same tone. The musical scale now in use arose to fit the needs of keyed instruments. The voice and stringed instruments can give the natural scale with many more intervals. Pitch has mathematical niceties, and its standard is a variable quantity. Philosophical pitch is determined by subdividing a wire that vibrates once a second. The variety of musical instruments has resulted from employing different vibrating substances, and from exciting vibration in these by several methods. Six classes of vibrations are noted: first, the vibrations of strings; second, of reeds; third and fourth, of elastic membranes; fifth, of solid elastic substances; and, sixth, "the vibrations of air upon itself in a confined space."

A consideration of orchestral instruments naturally follows. These are grouped as the string band, the "wood-wind," and the brass band. In each of these divisions are found four or more instruments that correspond to the soprano, alto, tenor, and bass in a vocal quartet. The modern orchestra dates from 1600; for, although the ancients used many instruments, they performed only unison-music, "while our idea of orchestral music is essentially part-music."

Rhythm, notation, marks of expression, and musical embellishments are fully illustrated. Musical form is next analyzed and traced to an origin in the old dances. The suite was "at first a set of dance-movements." In a study of figures and phrasing, the author points out that the leit-motif so characteristic of Wagner was first used by Mozart in Don Giovanni. Among the musical forms afflicted with changeable definitions is the symphony, now understood as a sonata for orchestra, but in the early part of the last century known as a prelude, interlude, or postlude. The development of the sonata, its various movements and dependent forms, follows, the more important of these being the concerto and classical overture.

The Catholic mass is named as the earliest vocal form. Some vocal forms are the offspring of instrumentation, such as the aria and rondo. Vocal music of any character may be written either in the strophe form, which repeats the music of one verse, or as an art-song, in which the music interprets the poem from beginning to end. The canon, the fugue, and, finally, modern dance forms are subjects of special study.

In conclusion, the author recommends to those wishing to become earnest musicians, ensemble-playing and score-reading. The German language should be acquired for the philosophy and literature of music, but Italian is most important to the vocalist. "Bach should be faithfully studied by every musician," since in him "the intellectual and emotional are so well balanced."

exists that heavy cannonading and great fires bring on rain. In some places it has been noticed often that a clear morning on the 4th of July has been followed by rain, and this has been attributed to the explosive celebration of the day. Mr. Powers has written his book to furnish definite evidence in support of the belief that rain can be produced by means of artillery, and to advocate the making of experiments by the Government in order to obtain certain proof in regard to it. His evidence consists of a record of those battles in our Mexican and civil wars in which artillery was largely used and which were followed by rain, giving the chief circumstances in each case. An appendix contains letters from army officers, transcripts from diaries, etc., supporting this record. In regard to the fact that artillery-firing does not always bring rain, the author says that the chief