In the middle of these speculations, he suffered a dark experience. He fell, for the first time in his life, into ill-health. His vitality and nervous force were great, and though soon depleted were soon recuperated; but the new and ardent interests of the university had appealed to him on many sides; he worked hard, took violent exercise, and filled up every space of time with conversation and social enjoyment; he had no warning of the strain, except an unaccustomed weariness, of which he made light, drawing upon his nervous energy to sustain him; the wearier he grew, the more keenly he flung himself into whatever interested him, learning, as he thought, that the way to conquer lassitude was by increased exertions, the feeling of fatigue always passing off when he once grew absorbed in a subject. He took to sitting up late and rising early, and he had never seemed to himself more alert and vigorous in mind, when the collapse came. He was suddenly attacked, without warning, by insomnia. One night he went to bed late, and found it difficult to sleep; thoughts raced through his brain, scenes and images forming and reforming with inconceivable rapidity; at last he fell asleep, to awake an hour or two later in an intolerable agony of mind. His heart beat thick and fast, and a shapeless horror seemed to envelop him. He struck a light and tried to read, but a ghastly and poisonous fear of he knew not what, seemed to clutch at his mind. At last he fell into a broken sleep; but when he rose in the morning, he knew that some mysterious evil had befallen him. If he had been older and wiser, he would have gone at once to some sensible physician, and a short period of rest would probably have restored him; but the suffering appeared to be of so purely mental a character, that he did not realise how much of it was physical. For that day and for many days he wrestled with a fierce blackness of depression, which gradually concentrated itself upon his religious life; he became possessed by a strong delusion that it was a punishment sent to him by God for tampering with freedom of thought, and little by little a deep moral anxiety took hold of him. He searched the recesses of his heart, and ended by painting his whole life in the blackest of colours.