The Irish Church bishoprics differed from the Romish in that they were held by hereditary succession, after the custom of ancient nations. All bishops were married. Prior to the introduction of the Christian system in Ireland the Sabian ceremonial had been succeeded by the Druidical, upon which had been engrafted that of the Culdees, and notwithstanding the fact that the Romish Church gradually usurped the ecclesiastical functions in Ireland, the last named people who for ages had been regarded as the depositaries of the ancient faith and the ancient system of laws, were highly respected by the people for their sanctity and learning. Many of the Greek and Roman writers who have dealt with this subject agree in ascribing to the Druids a high degree of scientific knowledge and mechanical skill. The principles of justice set forth in their judicial system, their love of learning, and the standard attained in the sciences and arts, prove the early people of Ireland to have been equal if not superior to any of the early historic nations. In referring to the number and magnitude of the monumental remains in Ireland, and while commenting on the mechanical skill of the Druids, the Rev. Smedley says: "I was present at the erection of the Luxor Obelisk in Paris, and yet I think that I would have felt greater emotion if I had witnessed the successful performance of the old Celtic engineer who placed on its three pedestals of stone the enormous rock which constitutes the Druidical altar here at Castle May." It is believed that this people understood the art of mining and that they were acquainted with the use of iron. The following is an extract from one of Hamilton's letters on the Antrim coast: