(3) The printed "Papers by G.B. Airy" are bound in 14 large quarto volumes. There are 518 of these Papers, on a great variety of subjects: a list of them is appended to this history, as also is a list of the books that he wrote, and one or two of the Papers which were separately printed. They form a very important part of his life's work, and are frequently referred to in the present history. They are almost all to be found in the Transactions of Societies or in newspapers, and extend over a period of 63 years (1822 to 1885). The progress made in certain branches of science during this long period can very fairly be traced by these Papers. (4) His private correspondence was large, and like his other papers it was carefully arranged. No business letters of any kind are included under this head. In this correspondence letters are occasionally found either dealing with matters of importance or in some way characteristic, and these have been inserted in this biography. As already stated the Autobiography left by Airy is confined almost entirely to science and business, and touches very lightly on private matters or correspondence. (5) The letters to his wife are very numerous. They were written during his occasional absences from home on business or for relaxation. On these occasions he rarely let a day pass without writing to his wife, and sometimes he wrote twice on the same day. They are full of energy and interest and many extracts from them are inserted in this history. A great deal of the personal history is taken from them. (6) All correspondence in any way connected with business during the time that he was Astronomer Royal is to be found at the Royal Observatory. It is all bound and arranged in the most perfect order, and any letter throughout this time can be found with the greatest ease. It is very bulky, and much of it is, in a historical sense, very interesting. It was no doubt mainly from this correspondence that the Autobiography, which so far as related to the Greenwich part of it was almost entirely a business history, was compiled. The history of the early part of his life was written in great detail and contained a large quantity of family matter which was evidently not intended for publication. This part of the Autobiography has been compressed. The history of the latter part of his life was not written by himself at all, and has been compiled from his Journal and other sources. In both these cases, and occasionally in short paragraphs throughout the narrative, it has been found convenient to write the history in the third person. 2, THE CIRCUS, GREENWICH. NOTE. The Syndics of the Cambridge University Press desire to express their thanks to Messrs Macmillan & Co. for their courteous permission to use in this work the steel engraving of Sir George Biddell Airy published in _Nature_ on October 31, 1878. TABLE OF CONTENTS.