His health had probably been impaired by his earlier exertions; but the intense mental labour expended on the arithmetical machine appears to have completely undermined his constitution, and to have laid the foundation of those acute bodily sufferings which cruelly afflicted him during the remainder of his life. His friends, with the hope of checking the evil, sought to withdraw him from his studies, and tempted him into various modes of relaxation. But the remedy was applied too late. The death of his father in 1651, and the retirement of his unmarried sister from the world to join the devout recluses of Port Royal-des-Champs, released him from all restraint. He sadly abused this liberty, until the frightful aggravation of his complaints obliged him to abandon altogether his scientific pursuits, and reluctantly to follow the advice of his physicians, to mix more freely in general society. He obtained some relief from medicine and change of habits; but, in 1654, an accident both made his recovery hopeless, and destroyed the relish which he had begun to feel for social life. He was in his carriage on the Pont de Neuilly, at a part of the bridge which was unprotected by a parapet, when two of the horses became unruly, and plunged into the Seine. The traces broke, and Pascal was thus saved from instant death. He considered that he had received a providential warning of the uncertainty of life, and retired finally from the world, to make more earnest preparation for eternity. This accident gave the last shock to his already shattered nerves, and to a certain extent disordered his imagination. The image of his late danger was continually before him, and at times he fancied himself on the brink of a precipice. The evil probably was increased by the rigid seclusion to which from this time he condemned himself, and by the austerities which he inflicted on his exhausted frame. His powerful intellect survived the wreck of his constitution, and he gave ample proof to the last that its vigour was unimpaired. In his religious opinions he agreed with the Jansenists, and, without being formally enrolled in their society, was on terms of intimate friendship with those pious and learned members of the sect, who had established themselves in the wilds of Port Royal. His advocacy of their cause at a critical time was so important to his fame and to literature, that a few words may be allowed on the circumstances which occasioned it.