Prof. G. B. Airy on the Planet exterior to Uranus. 511 



that this acid passes off with the perspiration of the body 

 after strong exercise and heating. 



According to the knowledge we possess concerning the fat 

 of plants and of animals, the combinations of the volatile and 

 non- volatile acids are with oxide of lipyle. A person the least 

 accustomed can with ease distinguish by their smell the dif- 

 ference between the fat of oxen, of pigs, or of fowls, particu- 

 larly when the fat is heated to the melting-point, but still the 

 composition of them all is the same. If the fat is washed 

 and the acids separated, it is no longer possible to distinguish 

 between them (butter is an exception). During the washing 

 the substances disappear which are characteristic of the dif- 

 ferent fats ; they appear to have volatilized or to be decom- 

 posed. The substance to which the peculiar smell of the fat 

 is due has not yet been isolated. It is possible that it is the 

 corresponding oxide of lipyle combination of the volatile fatty 

 acids. 



LXXII. Account of some Circumstances historically con- 

 nected with the Discovery of the Planet exterior to Uranus. 

 By G. B. Airy, Esq., Astronomer Royal*. 



JT has not been usual to admit into the Memoirs of this 

 A Society mere historical statements of circumstances which 

 have occurred in our own times. I am not aware that this is 

 a matter of positive regulation: it is, I believe, merely a rule 

 of practice, of which the application in every particular in- 

 stance has been determined by the discretion of those officers 

 of the Society with whom the arrangement of our Memoirs 

 has principally rested. And there can be no doubt that the 

 ordinary rule must be a rule for the exclusion of papers of 

 this character; and that if a positive regulation is to be made, 

 it must absolutely forbid the presentation of such histories. 

 Yet it is conceivable that events may occur in which this rule 

 ought to be relaxed ; and such, I am persuaded, are the cir- 

 cumstances attending the discovery of the planet exterior to 

 Uranus. In the whole history of astronomy, I had almost 

 said in the whole history of science, there is nothing com- 

 parable to this. The history of the discoveries of new planets 

 in the latter part of the last century, and in the present cen- 

 tury, offers nothing analogous to it. Uranus, Ceres and Pallas 

 were discovered in the course of researches which did not 

 contemplate the possible discovery of planets. Juno and 

 Vesta were discovered in following up a series of observations 



* From the Proceedings of the Royal Astronomical Society for No- 

 vember 13, 1846. 



