^ Obliquity of the Ecliptic at Edinburgh. 451 



circle is like that used in the former observations, six inches, 

 having a telescope provided with eye glasses possessing 

 magnifying powers of 20 or 30. The circle seems, however, 

 to have a small bias or irregularity on inverting the tele- 

 scope after reversing the circle, amounting, at a maximum, 

 to about 5", and proportional to the sine of the zenith 

 distance, which has been allowed for. Further observations 

 will enable me to investigate this more exactly. 



1836. Mean obliquity for January 1st, from observations 

 made, 



June 14th 23 27 297 



„ 15 27 35-3 



„ 16 27 31-3 



17 . , 27 32-4 



j> 



„ 20 27 40-2 



„ 21 27 46-8 



„ 23 . 27 50-2 



„ 24 . 27 54-6 



„ 25 . 27 32-6 



„ 28 27 36-1 



Meanof the whole of these . 23 27 38-9 



Bessel gives 23 27 38-4 



My general tables give . . 23 27 39-4 



Though there are considerable discrepancies in the pre- 

 ceding observations, yet they are not greater than might 

 be expected, from the size of the instrument and power of 

 the telescope, especially in such unfavourable weather as 

 we had last June. They were reduced by the formulae 

 given in my last paper, in which there are one or two 

 errors of copying, and some typographical, but these com- 

 monly do not affecifc the accuracy of general formulae or final 

 results. I was able to get only two or three rather unsatis- 

 factory observations on the late equinox, which I conse- 

 quently think scarcely worth transmitting you. 

 I am, dear Sir, 



Yours sincerely, 



WILLIAM GALBRAITH. 



54, South Bridge. 



