A branch line runs northward to Birr or Parsonstown.
The fine castle of Birr, beside its historical interest, has gained celebrity on account of the reflecting telescope erected here (1828-1845) by William, third earl of Rosse.
A great battle is said to have been fought near Birr in the 3rd century between Cormac, son of Cond of the Hundred Battles, and the people of Munster.
The accounts of the observations given in these papers, however, were fragmentary; but in 1879-80 a complete account of them was published by the present earl ("Observations of Nebulae and Clusters of Stars made with the 6-foot and 3-foot Reflectors at Birr Castle from 1848 to 1878") in the Scient.
According to the legend the saint, accompanied by St Brendan of Birr, followed the king to Tara and solemnly cursed it, from which time it was deserted.