letter begging Mrs. Somerville to write an account of Newton’s _Principia_ and of La Place’s _Mécanique Céleste_. In reference to the latter book he wrote, “In England there are now not twenty people who know this great work, except by name, and not a hundred who know it even by name. My firm belief is that Mrs. Somerville could add two cyphers to each of these figures.” Mrs. Somerville was overwhelmed with astonishment at this request. She was most modest and diffident of her own powers, and honestly believed that her self-acquired knowledge was so greatly inferior to that of the men who had been educated at the universities, that it would be the height of presumption for her to attempt to write on the subject. The persuasions of Lord Brougham and of her husband at last prevailed so far that she promised to make the attempt; on the express condition, however, that her manuscript should be put into the fire unless it fulfilled the expectations of those who urged its production. “Thus suddenly,” she writes, “the whole character and course of my future life was changed.” One is tempted to believe that this first plunge into authorship was, to some extent, stimulated by a loss of nearly all their fortune which had a short time before befallen Mr. and Mrs. Somerville. Before authorship has become a habit, the whip of poverty is often needed to rouse a student to the exertion and labour it requires. The impediments to authorship in Mrs. Somerville’s case were more than usually formidable. In the memoirs she has left of this part of her life, she speaks of the difficulty which she experienced as the mother of a family and the head of a household in keeping any time free for her work. It was only after she had attended to social and family duties that she had time for writing, and even then she was subjected to many interruptions. The Somervilles were then living at Chelsea, and she felt at that distance from town, it would be ungracious to decline to receive those who had come out to call upon her. But she groans at the remembrance of the annoyance she sometimes felt when she was engaged in solving a difficult problem, by the entry of a well-meaning friend, who would calmly announce, “I have come to spend an hour or two with you.” Her work, to which she gave the name of _The Mechanism of the Heavens_, progressed, however, in spite of interruptions, to such good purpose that in less than a year it was complete, and it immediately placed its author in the first rank among the scientific thinkers and writers of the day. She was elected an honorary member of the Astronomical Society, at the same time with Caroline Herschel, and honours and rewards of all kinds flowed in upon her. Her bust, by Chantrey, was placed in the great hall of the Royal Society, and she was elected an honorary member of the Royal Academy of Dublin, and of many other scientific societies. It was a little later than this, in 1835, that Sir Robert Peel, on behalf of the Government,