With increase of health his zest for work increased also, and he addressed himself to a great historical task. The subject he selected was the Maid of Orleans. The preliminary studies were difficult in a place destitute of all aids to learning. His researches were not confined to the collection of all the printed material; in 1876 he had planned to search out the documentary sources wherever they were to be found, but before this he made close studies in the field of psychology and mental pathology. The work of Ruf on the subject, the learned chaplain of a lunatic asylum, attracted his attention, and he entered into communication with the author. Ruf’s great experience and philosophical acquirements were of great service to Gebler in his preliminary studies on Joan of Arc. But the project was not to be carried out. Just as he was about to write the second chapter, an essay of Berti’s at Rome occasioned him to enter on fresh studies on Galileo. Domenico Berti, who had examined the original Acts of Galileo’s trial, though, as his work shows, very superficially, spoke contemptuously of the German _savans_, comparing them with blind men judging of colours, as none of them had seen the original Acts in the Vatican. This had special reference to the document of 26th February, 1616, which the German writers on the subject, and Gebler among them, declared to be a forgery. Being a man of the strictest love of truth, this reproach induced him, in spite of his health, which had again failed, in May, 1877, to go to Rome, where he obtained access to the Vatican. For ten weeks, in spite of the oppressive heat, he daily spent fourteen hours in the Papal Archives, studying and copying with diplomatic precision the original Acts of Galileo’s trial. As the result of his labours, he felt constrained to declare the document in question to be genuine. Actuated only by the desire that truth should prevail, in the second part of his work, written at Rome, he without hesitation withdrew the opinion he had previously advocated as an error. His first work had made a flattering commotion in the literary world, but the additional publication called forth a still more animated discussion of the whole question, which the readers of this journal will not have forgotten. Gebler took part in it himself, and, then suffering from illness, wrote his reply from a sick bed.