The rocks of the ballast

You may have spent some time near a train track and you have been drawn to those fragments of rocks that appear among the rails. I am sure that many people will know what they are and, above all, what they are for, but for the people who have wondered what the hell that is, I bring this article to you. Although I hope also to surprise you who already knew it. Detail of a stretch of railroad track, where you see the ballast, or ballast, on which …