292 Prof. Bessel on the Greewaoich Observations. 



of the former, if held against the light, appear transparent in 

 some places, and exhibit a peculiar fibrous structux'e, which the 

 non-calcined graphite does not possess. Melted with nitre, 

 the graphite produces no vehement detonations, but is con- 

 sumed slowly, and the remaining salt dissolved without resi- 

 duum by water. I did not succeed in converting sulphate into 

 sulphite of potash by means of graphite. Thus then the gra- 

 phite in gray rasv iron is not what it has been supposed to be, 

 a combination of carbon and iron ; but pure carbon, or its 

 metallic base. Whether natural graphite be also a pure car- 

 bon-metal, or really a combination of carbon and iron, is yet 

 to be determined. 



XLIX. Extract from a Letter addressed by Professor Bessel 

 to Professor Schumacher, relating to the Greeivwicli Obser- 

 vations* , as criticized in the Philosophical Magazine for No- 

 vember and December 1824. 



'Vl/'HEN I had the pleasure of being 3four guest at Altona, 

 ^* you showed me the numbers of the Philosophical Ma- 

 gazine which contain a very severe censure of the Greenwich 

 observations for 1821. I saw this censure with some surprise, 

 because I had always considered the collection of observations 

 at Greenwich as singularly valuable, and as a rich source of as- 

 tronomical truths ; nor were you, I believe, of a different opi- 

 nion ; and we were perfectly agreed respecting the unimpor- 

 tance of the inaccuracies that were imputed to this work in the 

 two papers pubhshed in the 6iih volume of the Philosophical 

 Magazine. 



For those who are acquainted with the Greenwich observa- 

 tions, and who compare them with the critic's remarks, every 

 further explanation would be superfluous. But since it may be 

 supposed that these remarks will fall into the hands of many 

 persons not deeply versed in astronomy, I readily comply with 

 the request which you made, that I would commit to writing 

 our common view of the subject. I feel, as well as yourself, 

 the propriety of doing my best on the occasion, in order that 

 too great importance may not be attached to this censure of 

 an establishment, to which astronomy is indebted for a great 

 proportion of its advancement ; and that its importance cannot 

 be very great, is sufficiently shown by the facility with which 

 Mr. Olufsen has computed the declinations of the fundamen- 

 tal stars, as published in the Nachrichten, No. 73, from the 

 Gi'eenwich observations for 1822. 



* From the Astronomical and Nautical Collections in the Journal of 

 Science, &c. vol. xx. p. 108. — The passages within brackets are as given 

 in the Collections. 



The 



