We read in the Sixth Book of the _Q.N._ (230) that the author had previously, when a young man, composed a work upon Earthquakes. This, taken in connection with what precedes, and with what we know of the author’s character and interests, affords some ground for the conjecture that he may have worked intermittently at the subject at various periods of life. But no doubt the arrangement of the materials and the completion of the work belong to his latter years. He had by this time lost his hold upon Nero, and had practically retired from political activity. His trust in princes had been found misplaced. He was disappointed if not embittered. The discussion of public affairs was precluded. It was dangerous even to let one’s thoughts rest upon them. But there were consolations for political disappointment and inactivity. Recourse might be made to the contemplation of those great works and workings of Nature which are exempt from the caprices of human passion. The study of Nature was equally fitted to humble and to console; to it Seneca betook himself for refuge.[12] [12] “The Stoics affected to despise physical studies, or at any rate to postpone them to morals. Seneca shared this edifying but far from scientific persuasion. But after his final withdrawal from court, as the wonders of nature forced themselves on his notice, he reconsidered his old prejudice, and entered with ardour on the contemplation of physical phenomena” (Cruttwell, _op. cit._ 381). The _Q.N._ may, thus, have been composed at different dates, materials for it being gathered at various times as opportunity offered. But the final arrangement and systematisation belong to the last years of the author’s life, about the years 63 or 64. The publication may not have taken place until some time subsequently, and may have been carried out by Lucilius, who was Seneca’s literary executor. So much is certain, that the work as we have it is not the work as it left the author’s hand. Much time and ingenuity have been bestowed on attempts to restore the _Q.N._ to what may be supposed to have been its original form. The most casual reading of it as it stands, shows that it is full of inequalities. If the clue could only be recovered, much of its difficulty and obscurity would disappear. As it is, it abounds in abrupt transitions, interruptions of the logical sequence, repetitions, excrescences, and even irrelevancies and inconsistencies, which it can hardly be supposed that an author would have allowed to remain in a treatise prepared for publication.