Abstract In 1849, Robert Mallet gathered all the necessary components to perform his experiment to record ground motion. Nevertheless, he failed to record adequate data (see Chapter 1 ). Today, the goals of seismic experiments certainly are more ambitious, but possible failures can arise from the very same causes. The causes of Mallet's failure are obvious: weak source: Gunpowder is 50% less energetic than dynamite. low sensitivity of receiver: It takes a fairly large ground motion to create ripples that can be observed at the surface of a mercury bowl. high instrument noise: Poor firing-time control, limited clock accuracy, and observer reflex time add up to constitute a large imprecision (noise) in time measurement. lack of understanding of wave propagation: A phenomenon as complex as wave propagation cannot be understood from one single observation. In this chapter, I shall review briefly how the first three causes of Mallet's failure have been addressed in the past and shall discuss the way they are addressed today. I will try to refrain from predicting too much about how they could be addressed tomorrow. In Chapter 4 , I will discuss the last cause of Mallet's failure — lack of understanding of wave propagation.