77 



in its substance, after the vessels have been injected ; but this ap- 

 pearance the author ascribes wholly to extravasation in consequence 

 of rupture of the vessels. 



November 24, .1831. 



JOHN WILLIAM LUBBOCK, Esq. V.P. and Treasurer, 

 in the Chair. 



A paper was read, entitled, " Facts adduced in refutation of the 

 assertion that the Female Ornithorhynchus Paradoxus has Mammae." 

 By Sir Everard Home, Bart. F.R.S. 



The author, after a minute examination, in which he was assisted 

 by Mr. Hartshorn and Mr. Bauer, of three specimens of female or- 

 nithorhynchi sent to him by Governor Darling, could not discover 

 mammae, although these parts are represented as existing by Pro- 

 fessor Meckel. 



A paper was next read, entitled, " On an Inequality of long Pe- 

 riod in the Motions of the Earth and Venus." By George Biddell 

 Airy, A.M. Plumian Professor of Astronomy and Experimental 

 Philosophy in the University of Cambridge. 



The author had pointed out, in a paper published in the Philo- 

 sophical Transactions for 1828, on the corrections of the elements 

 of Delambre's Solar Tables, that the comparison of the corrections 

 of the epochs of the sun and the sun's perigee, given by the late 

 observations, with the corrections given by the observations of the 

 last century, appears to indicate the existence of some inequality 

 not included in the arguments of those tables. As it was necessary, 

 therefore, to seek for some inequality of long period, he commenced 

 an examination of the mean motions of the planets, with the view 

 of discovering one whose ratio to the mean motion of the earth 

 could be expressed very nearly by a proportion of which the terms 

 are small. The appearances of Venus are found to recur in very 

 nearly the same order every eight years • some multiple, therefore, 

 of the periodic time of Venus is nearly equal to eight years. It is 

 easily seen that this multiple must be thirteen; and consequently 

 eight times the mean motion of Venus is nearly equal to thirteen 

 times the mean motion of the earth. The difference is about one 

 24-Oth of the mean annual motion of the earth ; and it implies the 

 existence of an inequality of which the period is about 24-0 years. 

 No term has yet been calculated whose period is so long with respect 

 to the periodic time of the planets disturbed. The value of the 

 principal term, calculated from the theory, was given by the author 

 in a postscript to the paper above referred to. In the present me- 

 moir he gives an account of the method of calculation, and includes 

 also other terms which are necessarily connected with the principal 

 inequality. The first part treats of the perturbation of the earth's 

 longitude and radius victor ; the second of the perturbation of the 

 earth in latitude ; and the third of the perturbations of Venus de- 

 pending upon the same arguments. 



g2 



