iv 



Tennyson. In 1826 he was appointed Lncasian Professor of Mathe- 

 matics, but this professorship he soon exchanged for the Plumian, to 

 which he was appointed in 1828. According to the Calendar of that 

 date, his predecessor in office merely gave lectures in the first half of 

 the midsummer term, while those of the former Lucasian Professor 

 are only vaguely referred to. But these were greatly enlarged by 

 Mr. Airy, whose syllabus extends over forty-eight pages of print. 

 They comprise statics, dynamics, hydrostatics, and geometrical optics, 

 but their chief character seems to have been the theory of undula- 

 tions. Many of the experiments on polarised light whose mathe- 

 matical theory is given in his tract on the undulatory theory were 

 exhibited here. He appears to have been the first to introduce into 

 Cambridge studies the beautiful theories of Fresnel. With these as 

 subjects, treated in his own skilful manner, we need not wonder at 

 the popularity of his lectures. Even after he had become Astronomer 

 Royal, we learn from his first report to the Board of Visitors, that 

 application to the Admiralty had been made by several members of the 

 University and by the Plumian Professor to allow him to give another 

 course of lectures at Cambridge. 



Along with the Plumian Professorship Mr. Airy undertook the 

 duties of the Director of the Observatory. He at once entered on 

 these arduous duties with his usual energy. His efforts were well 

 seconded by the University, who at once raised the slender income 

 of the professorship to an amount nearly double its former value. 

 In the first volume of the 'Astronomical Observations ' he tells us 

 that he was induced to fix on a plan of publication very different 

 from that of the ' Greenwich Observations.' He remarks that the value 

 of unreduced observations is so small that to most persons they are 

 absolutely useless. Pew, who have not made observations, under- 

 stand how much time and calculation must be employed before they 

 can be applied to any useful purpose. On the average, the pre- 

 paratory steps and the observation of a transit occupy from five to 

 ten minutes, while the complete reduction and discussion of the 

 observations employ full half an hour. The professor even said that 

 if an offer was made of a mass of regular meridional observations un- 

 reduced, he w r ould not think it worth acceptance. In giving, there- 

 fore, the results, he was giving the produce of four or five times as 

 much labour, necessarily irksome, as if he gave merely the un- 

 reduced observations. The report for the year 1828 covered the 

 interval of five months' residence at the Observatory ; he had no 

 assistant, and every step from making the observations to revising the 

 proof-sheets had to be done by himself alone. Yet in April of the 

 following year the report was published with all the necessary reduc- 

 tions. This promptness is maintained in the succeeding years, and 

 excited the admiration of M. Quetelet, the Director of the Obser- 



