If the vibrations of two strings are as two to three, the second vibration of the first, corresponds with the third vibration of the latter, producing the harmony called, a fifth.
_Caroline._ So, then, when I strike the key-note with its fifth, I hear every second vibration of one, and every third of the other, at the same time?
_Mrs. B._ Yes; and the key-note, struck with the fourth, is likewise a concord, because the vibrations, are as three to four. The vibrations of a major third, with the key-note, are as four to five; and those of a minor third, as five to six.
There are other tones, which, though they cannot be struck together without producing discord, if struck successively, give us that succession of pleasing sounds, which is called melody. Harmony, you perceive, arises from the combined effect of two, or more concordant sounds, while melody, is the result of certain simple sounds, which succeed each other. Upon these general principles, the science of music is founded; but, I am not sufficiently acquainted with it, to enter into it any further.
We shall now, therefore, take leave of the subject of sound; and, at our next interview, enter upon that of optics, in which we shall consider the nature of light, vision, and colours.
1. (Pg. 146) What is wind, and how is it generally produced?
2. (Pg. 146) How do the winds blow, around the place where the air becomes rarefied?
3. (Pg. 146) What effect is likely to be produced where the winds meet?
4. (Pg. 147) In what part of the globe is the air most rarefied, and what is the consequence?
5. (Pg. 147) How do these winds change their direction as they approach the equator?
6. (Pg. 147) How are the trade-winds produced, and how far do they extend?
7. (Pg. 147) How is the equilibrium in the air restored?
8. (Pg. 148) How can contrary currents of air be shown in a room?
10. (Pg. 148) What is meant by a periodical wind?
11. (Pg. 148) What occasions the land and sea breezes, and where do they prevail?
13. (Pg. 149) How do they change, and what is the cause?
14. (Pg. 149) What is meant by their breaking up, and what effect is in general produced?
15. (Pg. 149) Why is the wind most variable in high latitudes?
16. (Pg. 150) Why is the wind apt to lessen about sunset?