| 摘要 |
Upper and lower casings, each provided with a dome and an annular portion, are fixedly coupled together. The coupling of the upper and lower casings is substantially water-tight. The upper casing is transparent. A disk is housed within the upper casing. A cut-out is securely fastened to the disk. Means for producing rotary motion of the disk and cut-out in response to movement of the upper and lower casings is suspended between the domes of the casings. One or more balls are located within the annular portions of the upper and lower casings and are freely movable therein.
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