BIOGRAPHICAL NOTICE. XXXV 



cedure is briefly sketched, and the final conclusions are stated in the fewest words and 

 simplest manner possible. No one unacquainted with the subject would imagine how 

 much careful research was represented by these few pages of results. The tables were 

 printed as a supplement to the Nautical Almanac for 1856. 



As Adams had not taken holy orders, his Fellowship at St John's College came 

 to an end in 1852, but he continued to reside in the college until February 1853, when 

 he was elected to a Fellowship at Pembroke College, which he retained till his death. 

 In the autumn of 1858 he was appointed Professor of Mathematics in the University of St 

 Andrews, and shortly afterwards, in the same year, he was elected Lowndean Professor of 

 Astronomy and Geometry at Cambridge, in succession to Peacock. He continued his 

 lectures at St Andrews, however, until the end of the session in May 1859. In 1861 

 he succeeded Challis as Director of the Cambridge Observatory. In 1863 he married 

 Eliza, daughter of Haliday Bruce, Esq., of Dublin, who survives him. 



In 1853 Adams communicated to the Royal Society his celebrated memoir on the 

 secular acceleration of the Moon's mean motion. Halley was the first to detect this 

 acceleration by comparing the Babylonian observations of eclipses with those of Albategnius 

 and of modern times, and Newton referred to his discovery in the second edition of the 

 Principia. The first numerical determination of the value of the acceleration is due to 

 Dunthorne, who found it to be about 10" in a century. Tobias Mayer obtained the value 6"'7, 

 which he afterwards increased to 9". Lalande's value was nearly 10". The discrepancies 

 were due to the eclipses selected, the results derived from the different eclipses being in- 

 consistent with one another. The history of the theoretical investigations relating to the 

 acceleration may be summed up as follows: In 1762 the French Academy proposed as the 

 subject of their prize the influence of a resisting medium upon the movements of the planets. 

 The prize was won by Bossut, who showed that the principal effect of such a medium 

 would be an acceleration in their motions, which would be much more sensible in the case 

 of the Moon than in that of the planets. In 1770 the question proposed was whether 

 the theory of gravitation could alone explain the acceleration. Euler obtained the prize, 

 but he was unable to discover any term of a secular character, and concluded that 

 the force of gravitation would not account for this inequality. The subject was proposed 

 again in 1772, Euler and Lagrange sharing the prize between them. The former came to 

 the same conclusion as before, attributing the acceleration to a resisting medium; the 

 latter did not carry the application of his formulas so far as to complete the investigation. 

 The prize was again offered for the same subject in 1774, the competitors being required 

 to examine whether the fact that the Moon appeared to have a secular acceleration, 

 while there was no sensible effect of this kind in the case of the Earth, could be ex- 

 plained by the theory of gravitation alone, taking into account not only the action of the 

 Sun and the Earth upon the Moon, but also the action of the other planets, and even 

 the non-spherical figure of the Moon and Earth. The prize was awarded to Lagrange, who, 

 after showing that none of the causes proposed would suffice to explain the secular variation 

 of the Moon, concluded that, if this variation is real, it must be produced in some other 

 manner, such as by a resisting medium. But as the existence of such a medium was not 

 confirmed by the motions of the other planets, and was even contradicted by the motion 

 of Saturn, which seemed to show a retardation, Lagrange expressed doubts with respect 

 to the reality of the lunar acceleration, resting as it does on observations of eclipses in 



