of Edinburgh, Session 1877-78. 
587 
levers. The lines were drawn on the paper by the plan of friction- 
less marking invented by Sir William Thomson, and used in his 
Siphon Recorder. A rise in the curve (on the page) corresponds to 
a hollow in the tinfoil. The arrow pointing from right to left, 
indicates the direction in which the tinfoil passed under the vibrat- 
ing pointer when the sounds were uttered. 
The authors hope soon to be able to communicate to the Society 
the results obtained by subjecting the experimentally drawn wave 
forms to harmonic analysis. 
Fig. 1 gives the curve made by the sound of oo, as in “ food/’ on 
Tig. 1. 
the note b ; fig. 2 is oo on f by the same voice ; and fig. 3 is a still 
Fig. 2. 
Fig. 3. 
higher oo by another voice. As the speed at which the phonograph 
was turned was very nearly the same in all the examples, the relative 
Fig. 4. 
pitches are approximately given by the lengths of the periods. 
