236 



Reports on Special Researches 



with respect to the constancy of magnetometer No. 87. It is also the practice to use new 

 vahies from time to time of the distribution coefficients P and Q, as derived from observa- 

 tions over a limited period. 



The observations for series II and III were made in the "absolute room," or "porch," 

 in the west end of the magnetic observatorj',^ and in a small wooden hut about 20 meters 

 southwest of the Observatory. The stone pier in the small wooden hut is designated as 

 "hut," the north pier in the absolute room as A'' (for D and H observations), and the south 

 pier in the absolute room as S (for / observations). 



There may have been some confusion in the precise marks observed upon during the 

 declination series. No. Ill, or possibly some source of disturbance was present; it will be 

 noticed that both the dechnation-difference (C. I. W.-Helwan) and the station-difference 

 have changed appreciably since 1911. Hence it is deemed best to mark the 1914 dechna- 

 tion-result in the final summary as doubtful. 



'All values are referred to N; A'' = "hut"+0'.5. 

 T.tBLE 12 B.Results of Horizontal-Intensity Comparisons at the Helwan Observatory {Series II). 



'All values are referred to N; iV="hut" 77. 



'It appears that in 1908, when Mr. Pearson made his observations, the "absolute room" was the room in the east end 

 of the magnetic observatory. 



