| Year | 1915 |
| Date | 02-Dec |
| Volume | 33 |
| Issue | 762 |
| Page | 459 |
| Category | General |
| Part | |
| Title | Elementary Principles of the Bi-Pendulum Harmonograph |
| Author | Bettesworth Page |
| Notes | Detail of the phonoscope, compound figures, why do the simple ratios describe the most symmetrical spirals? A near view of the vibrator, the phonoscope complete |