The Vatican Council and Its Definitions: A Pastoral Letter to the Clergy by Henry Edward Manning, Archbishop of Westminster, one of the fathers of the First Vatican Council.

The above link is to a digitized and OCRed copy of the book by Cardinal Manning on Vatican I. The book is searchable. But when you read it, you see the scanned image. Please download a copy and read or keep for reference and research.

Manning defends the infallible faith of Peter and his successors, as not only a definition of Vatican I, but also a perennial teaching of the Popes, Saints, and Magisterium.