174 



Introduction to the Seventh Section 



reflected image of this star reduced to 1820 from that point. 

 To the arithmetical mean of each series the reduction of the 

 basin of water to the centre of the instrument has been ap- 

 plied ; for the latter is 5*625 Paris feet higher than the former, 

 and therefore the reduction for the zenith distance z = 

 — 0'-1182 tang z. 



Upper Passage.— Circle East. 



