The theory of mechanical seismographs, as given by several authors, shows some important imperfections: a) It lacks generality; b) the term representing the effect on the instruments of the ground acceleration is introduced in the seismographs equations in a rather unsatisfactory way; c) the theory does not explain clearly what is obtainable from a seismogram concerning the ground movement; d) as little attention is paid on it to the case of transient motion, an erroneous feeling is created that even at this motion the seismograph displacements build up to infinite values when resonance is reached.
Taking all these imperfections into account a new treatment of the question is presented here with the aim to remove them in some measure.