Royal Astrojiomical Society. 229 



observations through which the errors of division must be deter- 

 mined, in order that their results may be also independent of the 

 influence of gravity. 



" It follows also from this that the astronomer who uses a circle 

 is in possession of the means of rendering his results entirely inde- 

 pendent of the influence of gravity ; and that results obtained by 

 different instruments, when this method is followed, must accurately 

 agree. It is likewise to be remarked, that the power of reversing 

 the axis is an advantage with which the independence of the zenith 

 distances of the influence of gravity is connected (and without which 

 such independence could not be obtained). 



" Although of no use in a practical point of view, it may not be 

 uninteresting to investigate the numerical result which the theory 

 now developed gives in a particular case, on the supposition of sym- 

 metry. For this purpose, I took the case which corresponds to the 

 dimensions of my 3-feet circle by Repsold, and found that one of its 

 radii, the direction of which corresponds to a zenith distance z, alters 

 in length about — 0"'2274 cosz : its extremity deviates from its di- 

 rection at the initial point about + 0''* 67 26 sins; ; and its direction 

 at the extremity of the arc from that at the initial point by 

 — 0"'5 124 sin z. Although the supposition of symmetry upon which 

 these results depend is probably only correct in respect of the exte- 

 rior figure of certain parts of the whole instrument, this calculation 

 may give an idea of the extent to which the influence of gravity will 

 attain ; an extent which, from the complicated nature of the problem, 

 we should not be able, without a calculation, to estimate. 



" You may easily suppose that the conclusion I have just obtained, 

 namely, that the attainment of any required degree of precision in 

 results depends only on the observer, appears to me to be the strong- 

 est motive for the zealous prosecution of observations. In the ever- 

 memorable days I passed with you at Collingwood, you expressed 

 the opinion, that the prospect of completely attaining the object of 

 any undertaking is of itself sufficient to render it in a high degree 

 attractive." 



VIII. A Letter from J. R. Crowe, Esq., British Consul- General 

 of Norway, concerning a Literary Society established at Alten, near 

 Hammerfest. Communicated (with a letter) by Dr. Lee. 



Mr. Crowe visited England in the summer of 1843, and gave in- 

 formation concerning the existence of a Society consisting of Swedes, 

 Englishmen and Germans, at Alten, near Hammerfest in Finmark, 

 under the patronage of a Swedish clergyman, the pastor of that di- 

 strict. This Society was in possession of some instruments which 

 had been left there by some French gentlemen of science who were 

 sent to Lapland by Louis Philippe a few years ago. Regular obser- 

 vations of the barometer and thermometer had been instituted ac- 

 cording to the plan suggested by Sir John Herschel, and Mr. Crowe 

 was of opinion that if an observatory could be established the Society 

 would cheerfully undertake the working of it. 



Dr. Lee munificently furnished the Society with an achromatic 

 transit instrument of 30 inches focal length, and an aperture of 2 



