Disturbances of the former kind lead to vibrations of harmonic type, whose amplitudes always remain small; but disturbances, whose wave-length exceeds the circumference, result in a greater and greater departure from the cylindrical figure.
The amplitudes of these tones are proportional to the products of a and b multiplied by X or µ.
If this be overlooked, a wrong impression may be derived as to the absolute amplitudes of the changes.
The amplitudes and phases of the temperature waves at different points are observed by taking readings of the thermometers at regular intervals.
The wave motion due to any element of the surface is called a secondary wave, and in estimating the total effect regard must be paid to the phases as well as the amplitudes of the components.
