of the Summer Solstice, 29 



solstice obtained by direct measurement, from the pole, with- 

 out the aid of the intermediate point above mentioned; and it 

 will be seen that the results do not in this case differ above a 

 quarter of a second from each other. 



There is indeed no other difference between these two me- 

 thods, but that, in the former case, the part of the arc Z P is 

 obtained rather more accurately, by a great number of obser- 

 vations both before and after the solstice, than could be done 

 in the short interval of time in which the solstice itself is ob- 

 served. 



By sixty observations of 7 draconis, of w':ich only three 

 differ so much as 1" from the mean, it appears that the zenith 

 point which I have assumed is 2', 18" ,64,, south of the mean 

 position of 7 draconis for the beginning of the year 1812, which 

 is tfie same quantity that is found by the observations with the 

 zenith sector, 1811. 



Mr. Trough TON is now occupied in making a zenith sector 

 upon a new and very simple principle, with which 1 have no 

 doubt that this distance may be determined with a much 

 greater degree of precision. 



Astronomers will immediately perceive that this arc, how- 

 ever accurately it may be mechanically determined, must 

 inevitably be subjtxt t^ whatever uncertainty still exists upon 

 the question of astronomical refractions; the instrument not 

 having been erected long enough to remove this uncertainty, 

 I have for the present employed Dr. Bradley's refractions, 

 such as thvfy have been used for many years in this Observa- 

 tory. Such alterations in this part of the calculation may 

 easily be made in future, as the advanced state of the science 

 may require^ 



