HALL, ABEliUATlON CONSTANT. 



87 



Clamp West, refleeteil, above pole. 



+26.000 .^S — 2.905 Ak 



- 2.905 +13.540 



+ 10.889 + 1.125 



[nn. 3] = 8,196 



AS 



rr 

 [VV] = 8.192 



-0.701" 



+0.245 



—0.334 



r = ±0.405. 



+10.889 "" 

 + 1.125 

 +11.777 



-tO.105' 

 ±0.114 

 ±0.1.54 



-3.420" 



-2.071 



+0.410 



wt. 

 14.8 

 12.4 



6.8 



= 

 = 

 - 



Clamp West, reflected, below pole. 



+28.00GAS — 5.006 Ak 



[nn. 31 = 6.966 



5.008 

 -11.727 



+ 16.931 

 + 2.126 



a5 

 Ak 



[vv] = 6.993 



+0.963" 



+0..563 



-0.273 



r - ±0.367- 



-11.727 IT 



+ 2.126 

 + 10.330 



±0.094" 



±0.089 



±0.153 



+0.680" = 

 —9.138 = 

 + 1.178 = 



Wt. 

 14.3 

 16.0 



5.4 



On looking over the residuals it will be seen that some are large. But 

 it is doubtful whether any could fairly be omitted. It will be observed, 

 also, that there are changes in the signs of the residuals which seem to 

 correspond to sudden changes in the structural condition of the instru- 

 ment. However, the observations above and below pole ought to eliminate 

 such changes. 



In combining the above results, therefore, probably the reflected obser- 

 vations should be omitted. If the mean is taken of the values derived 

 from direct observations we have 



Ak 



0.238'', or k = 20.683' 



As stated before, in handling the meridian circle hereafter, I hope to 

 be able to make frequent reversals, and improve somewhat the accuracy 

 of the observations. It requires one day's work with an assistant to re- 

 verse the instrument and readjust the microscopes. Microscopes of higher 

 magnifying power might be employed, also, for reading the circles, and it 

 is expected to make some improvement in this direction. 



19. — Latitude. 



To find the latitude from the Polaris observations the mean of the re- 

 sults reduced to 1900.0 can be taken, so that we have 



1900.0. 



A<fr for position of reflection basin = —0.02", 



