"Salviati: But if this is true, and if a large stone moves with a speed
of, say, eight while a smaller one moves with a speed of four, then when they
are united, the system will move with a speed of less than eight; but the two
stones when tied together make a stone larger than that which before moved with
a speed of eight. Hence the heavier body moves with less speed than the
lighter; an effect which is contrary to your supposition."