Proceedings of the Cambridge Philosophical Society. 867 



probably established that these depend on the masses and mutual actions 

 of the revolving bodies. 



After the meeting, the Rev. L. Jenyns gave an account, illustrated by 

 drawings, of the comparative anatomy of birds and mammalia, and of se- 

 veral remarkable particulars respecting the former class of animals. 



March 2, 1829. — The very Rev. the Dean of Ely in the chair. A me- 

 moir by Pierce Morton, Esq. of Trinity College, was read, " on ihe 

 focus of a conic section," in which the author pointed out the soHd con- 

 struction from which that point is derived. 



The reading of a paper by Professor Whewell was also begun, " on 

 the application of mathematical reasoning to some of the theories of Poli- 

 tical Economy," in which the author maintained, that, so far as that science 

 is founded on definitions and axioms, the shortest and most certain me- 

 thod of deducing its results is by the assistance of mathematical process. 



After the meeting, Professor Whewell gave an account of some of the 

 contrivances which have been employed in the use of the dipping needle, 

 and exhibited one of a construction in some respects new. 



Art. XXIX.— scientific INTELLIGENCE. 

 I. NATURAL PHILOSOPHY. 



ASTRONOMY. 



1. Mr Dunlops Observations on Enckes Comet. — Mr Dunlop discovered 

 at Makerston the celebrated comet of Encke, on the 26th of October. 

 His first observation gave its place about 16" or 18" of time greater in 

 right ascension, and about one minute farther north than its place in the 

 Ephemeris. Several observations which he made in November, and which 

 he has reduced, give nearly the same differences, and the observation of 

 December 7th, gives its place about 20" greater in right ascension, 

 and fully one minute from the north in declination than the calculated 

 place. Since the beginning of December it has been decreasing in bright- 

 ness ; but it is considerably higher than it was in 1 822. Mr Dunlop 

 measured the diameter of the chevelure on the 7th December, and found 

 it about five minutes. About the end of November he thinks it would 

 be about six minutes. The nebulous form is not round but rather fan- 

 shaped, with the condensation of the nebulous matter near the point or 

 apparent lower extremity. 



OPTICS. 



2. Supernumerary Rainbows. — In our last Number , p. 163, we committed 

 a strange oversight in stating that the supernumerary colours had not before 

 been seen in the secondary or outer bow. We have ourselves mentioned 

 them in the article Optics, in the Edinburgh EncychpoBdia, as seen by M. 

 Dicquemarre, and also Dr Young's explanation, which connects the phe- 

 nomenon with that of the colours of thin plates, {^Nat. PhiU vol. i. p. 470,) 

 applies to both* 



