The general recognition of the importance of vibration study, as a specialised branch of engineering science, is clearly reflected in the fact that each year sees the publication of a great number of papers on all aspects of vibration theory and practice. The theoretical papers most commonly describe new methods of analysis and calculation, and it is becoming increasingly difficult for the general engineer, who has neither the time nor the inclination to follow in great detail the development of all the specialised subjects, of which vibration study is only one, to retain in his mind a clear picture of the general strategy applicable to the attack on vibration problems, and to fit into this strategical scheme the tactical operations represented by the new methods.