If the intervals between the shocks are alternately t and t', and if the difference between t and t' is slight, we obtain the two notes t+t' and (t+t')/2. If the intervals between the shocks are alternately t, t', and t'', we obtain the two notes t+t'+t'' and (t+t'+t")/3. Disk No. 1 has-- On circle No. 1 12 holes, angular distances t=30° " " 2 24 " " " 15° " " 3 36 " " " 10° " " 4 36 " at irregular distances. " " 5 36 " distances t= 10½°, t'=l0°,t''=9½° " " 6 36 " " 11° 10° 9° " " 7 36 " " 16° 14° " " 8 36 " " 16½° 13½° Circle No. 8 produces the two notes of circles 1 and 2; circle No. 7 the same, but the low note is stronger than in 8. Circle 6 produces the notes of circles 1 and 3, and so does circle 5, but in the latter the low note is stronger than in 6. Circle 4 produces a noise approximating only to the note of circle 3. By pulling out one of the buttons of the wind chest, we admit the air through eleven holes at a time, having an angular distance of 30° and directing it against the corresponding circle of holes on the turning disk. If the arrangement of holes is not repeated identically twelve times on the same circle, we cannot, of course, make use of the above arrangements of holes of the wind tube, and we must then employ one of the movable brass tubes, which communicate with the interior of the wind chest by means of rubber tubes and stopcocks. The experiment with disk 1, circle 4, for example, requires the use of one of these two tubes, while the perforated wind tube of the wind chest may be used with all the other circles of the same disk. B. If t is much less than t', while t' is a multiple of t, the note (t+t')/2 disappears, and the notes t+t' and t are heard. Disk No. 2 has-- On circle No. 1 12 holes, distances 30° " " 2 36 " " 10° " " 3 48 " " 7½° " " 4 60 " " 6° " " 5 24 " " t= 5°, t'=25° " " 6 24 " 6° 24° " " 7 24 " 7½° 22½° " " 8 24 " 10° 20° Circle 8 produces the notes of circles 1 and 2; circle 7, those of 1 and 3; circle 6, those of 1 and 4; and circle 5, the note of circle 1 and of its sixth harmonic. C. If the same circular arc is divided into m and n equal parts; that is to say, if mt=nt', we obtain the notes m and n. Disk No. 3 has--