As a result No.

2 will sound clearly, and if your ears are keen you will at the same time hear No.6.In succession hold down the keys of 3, 4, 5, and 6, while you strike and release the fundamental No.

1.
If your piano is "in tune" you will probably hear No.

6 when holding the key of any other note of the series.
In a musical tone of rich quality the overtones just indicated are present in their fulness, while tone that is weak and thin is made so by the absence or weakness of the overtones.

I have stated that the quality of a tone depends on the _form_ of its vibrations, and that the form of its vibrations is determined by the character of the _resonator_.