108 Astronomical and, Nautical Collections, 



Young, in 1807, had made the magnetic pole 15° more northerly, 

 and 8° more easterly ; Biot 19° more northerly, and 50° more 

 easterly ! 



In the experiments on the diurnal variation both at Hammerfest 

 and at Spitzbergen, the needle seems to have passed its mean po- 

 sition about half an hour before noon and midnight. 



The dip sector, employed for observing the depression of the 

 horizon in the neighbourhood of the gulf stream, was found to afford 

 very correct results, but less irregular than might have been ex- 

 pected from the actual diversities of temperature of the sea and 

 air concerned in the refraction ; the error of the tabular dip never 

 amounting to two minutes. It was ascertained in Jamaica, by 

 some delicate thermometrical experiments, that the heat commu- 

 nicated by the sun's rays is very sensibly greater in the upper 

 regions of the atmosphere, than on the level of the sea. A num- 

 ber of important geographical and hydrographical notices, espe- 

 cially relating to the currents in the Atlantic, are contained in this 

 volume, together with appropriate charts. 



It is impossible to quit the subject of Captain Sabine's experi- 

 mental labours without giving the strongest testimony of applause 

 to his zeal and diligence and accuracy, and expressing a hope that 

 he may find both private and public motives for continuing his 

 exertions with equal ardour in the prosecution of further investi- 

 gations connected with the advancement of physical science. 



vi. Extract from a Letter addressed by Professor Bessel to Pro- 

 fessor Schumacher, relating to the Greenwich Observations. 



When I had the pleasure of being your guest at Altona, you 

 showed me the numbers of the Philosophical Magazine, which 

 contain a very severe censure of the Greenwich Observations for 

 1821. I saw this censure with some surprise, because I had al- 

 ways considered the collection of observations at Greenwich as 

 singularly valuable, and as a rich source of astronomical truths » 

 nor were you, I believe, of a different opinion; and we were per- 

 fectly agreed respecting the unimportance of the inaccuracies that 

 were imputed to this work in the two papers published in the 64th 

 volume of the Philosophical Magazine. 



