After having introduced the subject of scaling, specifically whether structures or machines can be built of arbitrarily large size while retaining the same resistance to fracture, Galileo continues the First Day of his Dialogues by inquiring about the source of strength of various materials. In what follows, Salviati, Sagredo and Simplicio discuss two possible reasons why material might cohere, ... [Show full abstract] or stick together. What are these two reasons? Are there any other possibilities? Their discussion quickly turns to the possibility of atoms, a topic brimming with seeming paradoxes, and the source of ancient philosophical disagreements dating at least as far back as Aristotle and Democritus—disagreements which persisted up to and beyond the time of Galileo.