Vlll 



engine of mathematics, he expresses his surprise at finding that a 

 satisfactory explanation could be offered for almost every inequality 

 recognised as sensible in works on physical astronomy. The book, 

 though well received, was, for many reasons, not so popular as his 

 tracts. In 1884, however, it received the honour of a second edition. 



In 1836-37 he was President of the Astronomical Society. In the 

 first of these years, when presenting the medal of the Society to 

 Herschel for his catalogue of nebulae and clusters of stars, he gave an 

 interesting account of the history and of the then ? state of our know- 

 ledge of these curious bodies. The next year the address was on the 

 perturbations of comets. 



The year 1835 was a great epoch in Mr. Airy's life, for he was 

 then appointed Astronomer Royal. How thoroughly he intended to 

 work the National Observatory is evident from his very first report, 

 for here we find traces of the reforms he intended to introduce ; the 

 arrangement of the volumes of observation was to be remodelled ; the 

 library improved ; a new equatoreal was suggested ; a magnetic 

 apparatus had already been acquired, and the site of a magnetic 

 observatory chosen. 



Remembering the views he had expressed on unreduced observa- 

 tions when he began work at the Cambridge Observatory, we 

 naturally inquire what he did with the vast mass of ancient observa- 

 tions which he found unreduced when he arrived at Greenwich. 

 This we learn gradually as we read his reports to the Board of 

 Visitors. In 1 84 L the observations of planets from 1750 to 1830 had 

 already been reduced to longitude and latitude, and every one had 

 been compared with the place computed from the best modern tables. 

 Sufficient time had not yet elapsed to allow of the reduction of the 

 lunar observations, for here 8000 places of the Moon had to be 

 deduced from observation, and 8000 places had to be computed in 

 duplicate from tables exhibiting the complicated results of the most 

 advanced modern theory. In extent and in importance this work 

 may be considered comparable to any that has yet been undertaken in 

 astronomy. In 1846 these lunar reductions were entirely completed. 

 One immediate result was that Hansen discovered two inequalities 

 of long period in the Moon's motion, produced by the attraction of 

 Venus, though some doubts were afterwards thrown on one of these 

 by Delaunay and Newcomb. For these reductions he received in 

 1846 a gold medal, and in 1848 a testimonial, from the Astronomical 

 Society. Sir John Herschel, in the latter of these years, after noting 

 that this work will remain to the latest posterity a monument of 

 national glory, remarked that we owe to other nations, and especially 

 to the French, the filling up of the great outline struck by Newton 

 with the analytical expressions of the laws of lunar and planetary 

 motion. This glory, he says, they have fairly won, and it is theirs. 



