Mr. Phillips on a neia Oxide of Manganese ; 4-c. 209 



mental results, it seems to be the justest and most natural in- 

 ference that can be drawn from those results. 



The matter has, however, been viewed diflFerently. The 

 lencrth of a degree of the parallel computed on the given sphe- 

 roid is 77835 metres : but if we substitute the astronomical 



xuiu la I (i^ 1742"-22 



in place of the geodetical amplitudes, we shall have y^jT^^g 

 X 77835 = 77886* metres for the mean length of a degree 

 between Marennes and Geneva ; and ^^^^.^^^ x 77835 = 77866 

 metresf for the mean degree between Marennes and Padua. 

 Now the differences between the mean degrees and the degree 

 on the assumed spheroid, which are considerable, arise solely 

 from the small differences between the geodetical and the 

 astronomical amplitudes, or rather, as we are warranted in 

 saying, from the errors of the astronomical amplitudes. If 

 the small intervals of time, namely 1"-142 and 1"-219, by which 

 the geodetical exceed the astronomical amplitudes, may be 

 ascribed either wholly or m part to errors of observation, it 

 will be allowed that the lengths, 51 metres and 31 metres, 

 by which the degree on the assumed spheroid exceeds the 

 mean degrees answering to the astronomical amplitudes, rest 

 either on no authority, or on doubtful authority. Very little 

 stress can therefore be laid on the new compression of the earth 

 deduced from the combination of the mean degrees, viz. 

 77886 and 77866 metres, with degrees of the meridian already 

 known. It may very well happen that this method of pro- 

 ceeding, instead of bringing us nearer the truth, may lead us 

 away from it. The conclusion that follows directly and na- 

 turally from the measurement of the parallel, is m favour of the 

 supposition that the earth is a spheroid of revolution having the 

 compression indicated by the lengths of the meridional arcs. 

 Feb. 13, 1828. J- IvORY. 



I 



XXXII. On a new Compound of Oxygen and Manganese ; "with 

 Remarks on Dr. Turner's Memoir on the Oxides of that Metal. 

 Bi/ R. Phillips, F.R.S. L. ^ E. Sfc. 



N noticing Dr. Turner's " Elements of Chemistry" (Phil. 

 Mag. and Annals, vol. i. p. 379), I have stated it as my 

 opinion in opposition to his, that when peroxide of manga- 

 nese is heated in sulphuric acid, it is converted merely into 

 deutoxide. In a paper on the oxides of manganese, which 

 Dr. Turner was so good as to send to me, and which has been 



• Conn, det Terns, p. 29.3. \ Ibid. p. 291. 



N.S. Vol. 5. No. 27. March 1829. 2 E printed 



