Why are granite stones on the railway track?

Many black colored granite stones have been seen lying on the railway track. If you want to know why these stones are there, many people will say that these broken stones are given to control the excess heat generated in the collision of the train wheels and the lower iron balls. Those who are called Ballet. But there are other reasons besides this. Find out what the reasons are
When the train passes over the iron bars, all the pressure is transmitted on the wooden leg through the iron rod. The ballast is given to the pressure in order to maintain the balance of the wood in its own position.
Because of the stones, the train line is slightly above the ground. So there is less chance of drowning in excess rain.