overlooked in the study of his philosophy. His last piece of all, _Decameron physiologicum_ (_E.W._ vii. 69-180), in 1678, was a new set of dialogues on physical questions, most of which he had treated in a similar fashion before; but now, in dealing with gravitation, he was able to fire a parting shot at Wallis; and one more demonstration of the equality of a straight line to the arc of a circle, thrown in at the end, appropriately closed the strangest warfare in which perverse thinker ever engaged.[19] Later Years. We must now turn back to trace the fortunes of Hobbes and his other doings in the last twenty years of his life. All these controversial writings on mathematics and physics represent but one half of his activity after the age of seventy; though, as regards the other half, it is not possible, for a reason that will be seen, to say as definitely in what order the works belonging to the period were produced. From the time of the Restoration he acquired a new prominence in the public eye. No year had passed since the appearance of _Leviathan_ without some indignant protest against the influence which its trenchant doctrine was calculated to produce upon minds longing above everything for civil repose; but after the Restoration "Hobbism" became a fashionable creed, which it was the duty of every lover of true morality and religion to denounce. Two or three days after Charles's arrival in London, Hobbes drew in the street the notice of his former pupil, and was at once received into favour. The young king, if he had ever himself resented the apparent disloyalty of the "Conclusion" of _Leviathan_, had not retained the feeling long, and could appreciate the principles of the great book when the application of them happened, as now, to be turned in his own favour. He had, besides, a relish for Hobbes's wit (as he used to say, "Here comes the bear to be baited"), and did not like the old man the less because his presence at court scandalized the bishops or the prim virtue of Chancellor Hyde. He even went the length of bestowing on Hobbes (but not always paying) a pension of L100, and had his portrait hung up in the royal closet. These marks of favour, naturally, did not lessen Hobbes's self-esteem, and perhaps they explain, in his later writings, a certain slavishness toward the regal authority, which is wholly absent from his rational demonstration of absolutism in the earlier works. At all events Hobbes was satisfied with the rule of a king who had appreciated the author of _Leviathan_, and protected him when, after a time, protection in a very real sense became necessary. His eagerness to defend himself against Wallis's imputation of disloyalty, and his apologetic dedication of the _Problemata physica_ to the king, are evidence of the hostility with which he was being pressed as early as 1662; but it was not till 1666 that he felt himself seriously in danger. In that year the Great Fire of London, following on