BIOGRAPHICAL NOTICE. xxxix 



Additions to the Connaissance des Temps for 1864, in which the place occupied by 

 Adams's memoir in the history of gravitational astronomy is so well summed up that 

 it may be permissible to quote the passage in its entirety: 



" L'apparitiori du me'moire de M. Adams a 6t^ un veritable e've'nement : c'e"tait toute 

 une revolution qu'il ope'rait dans cette partie de 1'astronomie theorique. Aussi le re'sultat 

 qu'il renfermait fut-il vivement attaque' ; on ne voulait pas 1'admettre, et on ne manquait 

 pas de raisons a donner pour cela. II est, disait-on, en disaccord complet avec les ob- 

 servations ; il ne tend a rien moins qu'a enlever a Laplace 1'honneur d'une de ses plus 

 belles de'couvertes ; il est base d'ailleurs sur une analyse fautive et erronee. Mais parmi 

 toutes ces raisons il n'y en avait pas une bonne ; et la persistance avec laquelle elles 

 ont dtd prdsentees et soutenues a produit un effet diamdtralement oppos6 a celui qu'on 

 en attendait : les confirmations de ce re'sultat tant contest^ se sont accumule'es a un tel 

 point, qu'il serait difficile de trouver dans les sciences une ve'rite' mieux dtablie que ne 

 Test maintenant celle que M. Adams a mise en avant le premier dans son me'moire de 

 1853. Toutes les objections qui avaient e'te' formule'es sont tombees d'elles-memes. 

 L'analyse de'clare'e fautive et erronee a et^ reconnue exacte. L'accord ou le disaccord du 

 re'sultat the'orique avec les indications fournies par les observations n'a plus die" regard 6 

 comme un moyen de contrdler 1'exactitude de ce re'sultat theorique. Si le disaccord 

 annonce' existe bien re'ellement, on en conclut simplement que la cause assignee par 

 Laplace a 1'acceldration seculaire du moyen mouvement de la Lune ne produit pas seule 

 la totalitd du phenomene et on ne trouve dans ce disaccord rien qui soit de nature a 

 amoindrir la de'couverte de 1'illustre gdometre francais." 



These sentences derive additional interest from the fact that they were written by 

 one who was himself the author of the most comprehensive and elegant method by which 

 the lunar problem has ever been treated, and who was the first to recognise the accuracy 

 of Adams's result. In 1866 the Gold Medal of the Society was awarded to Adams for his con- 

 tributions to the development of the Lunar Theory, the address on the occasion being delivered 

 by Mr De la Rue. In the preparation of this very able address, which contains an excellent 

 history of the problem of the secular acceleration, Mr De la Rue had the invaluable assistance 

 of Delaunay. To complete the account of Adams's connexion with the secular acceleration, 

 it should be stated that in 1880, thirty-seven years after Adams's memoir, Airy com- 

 municated to the Society a paper on the theoretical value of the acceleration (Monthly 

 Notices, vol. xl. p. 368), in which he obtained the value of 10"'1477. At the next meeting 

 of the Society Adams pointed out that in Airy's method of treatment certain terms were 

 omitted, the effect being that the expression for the coefficient was reduced to its first 

 term, so that the result necessarily agreed with Laplace's. Subsequently, taking into 

 account these terms, Airy obtained the value 5" - 4773. Adams took the occasion of the 

 matter being thus again raised to communicate to the Society the investigation of the 

 acceleration which he had been in the habit of giving in his lectures. 



In the Monthly Notices for April 1867 Adams published an account of the results 

 he had obtained with respect to the orbit of the November meteors. Professor H. A. 

 Newton had concluded that these meteors belong to a system of small bodies describing 

 an elliptic orbit about the Sun, and extending in the form of a stream along an arc 

 of that orbit of such a length that the whole stream occupies about one-tenth or 

 one-fifteenth of the periodic time in passing any particular point. He showed that the 



A- / 



